a holies ee Pee Re von Srey i ae Sa
Digitized by the Internet Archive
in 2010 with funding from
University of Toronto
htto://www.archive.org/details/bulletinofmuseumO06harv
.
J
l- .
—
4 ,
x, i,
‘
¢
j
n
.
a
.
i
i:
|
.
'
.
.
i
-
’
.
we 4
\
~>
‘
>
_ ta
v
:
‘ 7
fF
'
’
i
ae
c
pes
“MUSEUM OF Fin voces ZOOLOGY
BULLETIN
OF THE
ar {
AT
HARVARD COLLEGE, IN CAMBRIDGE.
VOL. VI.
Parr I.—fes.. i—11.
CAMBRIDGE, MASS., U.S. A.
1879-1880.
UNIVERSITY Press:
Joun WiLson AND Son, CAMBRIDGE.
613'708
A ae
CONT E iets
PART IL.
No. 1.—List of Dredging Stations occupied by the United States Coast
Survey Steamers “ Bibb,” ‘ Hassler,” and “ Blake,” from 1867 to 1879.
B. Perrce and C. P. Patrerson, Superintendents ‘
No. 2. — Ophiuride and Astrophytide of the “ ot Wie aca Expedition. By
T. Lyman. Part II. (9 Plates.) . : ; : : ;
No. 38. — Reports on the Dredging Operations of the United States Coast Sur-
vey Steamer “Blake.” V. General Conclusions from a Preliminary Ex-
amination of the Mollusca. By W. H. Datu
No. 4.— Reports on the Dredging Operations of the United States Coast Sur-
vey Steamer “ Blake.” VI. Report on the Corals and Antipatharia. By
L. F. Pourtaes. (3 Plates.) 2 : : A ; : :
No. 5. — The Ethmoid Bone in the Bats. By H. ALLEN
No. 6.— On certain Species of Chelonioide. By S. Garman.
No. 7.— Contributions to a Knowledge of the Tubular Jelly-Fishes. By J.
W. Fewxes. (38 Plates.) , = . : : :
No. 8. — Letter No. 4 to C. P. Patterson, Superintendent of the United States
Coast Survey, on the Dredging Operations of the United States Coast Sur-
vey Steamer “‘ Blake.” By A. Acassiz
No. 9. — Reports on the Dredging Operations of the United States Coast Sur-
vey Steamer “ Blake.” VII. Description of a Gravitating Trap for obtain-
ing Specimens of Animal Life from Intermedial Ocean-Depths. By C. D.
Si1gsBEE. (1 Plate.) A : ‘ : ah tt
No. 10.— On some Points in the Structure of the Embryonic Zoéa. By W.
Faxon. (2 double Plates.) . ; :
No. 11.—New Species of Selachians in the Museum Collection. By S.
GARMAN .
PAGE
121
128
127
147
155
159
167
No. 1.— List of Dredging Stations occupied by the United States
Coast Survey Steamers “Corwin,” “Bibb,” “Hassler,” and “Blake,” -
from 1867 to 1879. BENJAMIN PEIRCE and CaRLite P. Pat-
TERSON, Superintendents of the Coast Survey.
THE following stations were occupied by the U.S. Coast Survey
Steamer “Corwin,” Acting-Master R. Platt, U. 8. N., commanding, in
1867, in connection with a survey for a telegraph cable between Key
West and Havana. The dredging operations were in charge of L. F.
Pourtalés, Assist. U. S. Coast Survey. The expedition was cut short by
the breaking out of yellow-fever on board.
Date. Position. Depth. Locality.
May 17 1 90-100 fms. 5m. 8.S8.W. of Sand Key, Fla.
“ 24 2 270% 1.6 m. from Chorrera, Cuba.
“« 95 3 350 © 27. a a
29 4 20: 1.6 m. ee 66
The dredgings in 1868 and 1869 were made on board the U. S. Coast
Survey steamer “ Bibb,” Acting-Master R. Platt, U.S. N., commanding,
by L. F. Pourtalés, Assist. U. S. Coast Survey. They are all comprised
jn the Florida Straits between Tortugas and Cape Florida. (See U. 8S.
Coast Survey, General Coast Chart No. X., Coast Survey Report for
1850.)
1868, No. of Dredging. Fms. Locality.
April 23 2d position 195 Off Sombrero.
6 66 3d (73 115 6 “
May 1 7 111 “ ee
(74 66 6 1 91 74 6c
ce 6c 5 1 11 oe ‘cc
6e “cc 4 il 52 (43 “cc
“ “ 3 183 « ‘6
66 6c 9 962 (74 “cc
¢e 66 1 51 7 “ 74
se 1 19 Off Bahia Honda.
é ‘“ 4 75 «“ ‘“
é “ 5 95 “ ‘“
VOL. VI. — NO. 1.
1868,
May 4
ac “ce
“ 66
6c it
bb “ce
“ is
ae 66
be 6
“e ec
be ee
66 46
ac 66
46 66
4c sé
+c 6
ge sty
be 4e
4c “e
&6. 66
66 g
Lad 6e
Lad 4c
ee ee
46 4é
a 66
6 ¢e
&é 46
Lad ¢e
oe ee
46 “ec
46 24
sé sc
iad 74
46 6e
$6 oe
“11
sé ec
ee “é
iad sé
sé zs
sc se
46 ‘é
sé “6
“6 ce
BULLETIN
. of Dredging. Fms.
6 105
7 100
9 119
10 128
11 176
12 324
13 418
1 16
3 43
4 55
5 75
6 83
7 98
8 94
9 100
1 sr
3 150
4 135
5 266
2 34
4 67
+) 80
6 93
é 96
8 101
9 106
10 106
11 116
12 123
13 125
14 125
16 139
ily 147
18 298
19 237
2 26
3 54
4 67
5 82
6 94
7 103
9 119
10 119
11 128
OF THE
Off Bahia Honda.
Locality.
66
1868.
May 1
66 ‘6
66 66
66 6é
66 66
66 66
“ec 66
sé 66
46
66 66
66 66
6c 66
66 66
“16
66 66
66 66
66 66
1869.
Jan. 15
66 66
6é 66
“6 66
66 66
“« 16
66 66
66 66
66 6
66 ‘6
66 66
66 66
66 66
66 66
66 66
66 66
i Fe
66 66
66 66
oh odd
66 73
66 66
66 66
66 ce
6c 66
66 66
MUSEUM OF COMPARATIVE ZOOLOGY.
No. of Dredging.
12
13
14
15
16
17
19
20
—_
SO MND OP &© | aw oo be
—
if
ry
bo
&
Cr GPa OO KH So we KH
i)
—_
i)
Fms.
127
123
134
143
138
154
306
248
100
100
100
100
100
120
120
120
120
6-7
13
17
34
260
80-32
35
36
36
35
35
37
37
34
43
42
43
124
502
25
60
115
214
306
389
468
Off
Locality.
Sand Key.
66
W. of Tortugas.
66
66
66
oe
No. of Dredging.
1
wondrF nF OH OAD OP & bo
Several casts.
oPowoNnDreeE NFP ARP WON RP OR WR OOP WN RB OD OT Oo bt
BULLETIN OF THE
Fms.
13
12-15
107
132
140
296
333
105
122
122
125
125
90
125
327
368
405
50
125
138
325
87
450
638
815
40
45
49
70
60
Locality.
Between Rebecca Shoal
Kast Key.
S. of Rebecca Channel.
12m. W. of Marquesas. »
Off the Quicksands.
Off Marquesas.
66 66
S. of Marquesas.
66 66
66 66
Off Cojima, near Havana.
Off Cruz del Padre, Cuba.
and
Off Double-headed Shot Keys.
Off Conch Reef.
Off French Reef.
Off the Elbow Reef.
6 73
Off Carysfort Reef.
MUSEUM OF COMPARATIVE ZOOLOGY.
1869. No. of Dredging. Fms. Locality.
March 21 6 48 Off Carysfort Reef.
66 66 7 40 6c 6
ss 66 8 35 66 66
ae “ 9 12 Off Turtle Harbor.
> ee 1 63 Off Carysfort Reef.
66 “6 2 116 “é 66
66 66 8 138 66 66
a A (Empty.) 293 “6 “6
66 ‘é 5 317 66 “6
rT rT 6 320 “ ‘6
= ae 7 351 <é i
6c 31 1 52 6é €é
“6 66 ») 117 sé 66
¢é eé 3 206 6é 6é
A =¢ 4 349 “ ff
April 1 2&3 9 Off Orange Key, Bahamas.
se 3 1 15 Off French Reef.
6é ee 2 87 6é 6é
66 66 38 44. cé 6é
ée¢ cé 4 6¢ 6é
écé 6é 5 75 &é 6¢é
66 ¢é 6 10 66 cé
- 21 1 135 Off Key West.
66 &é 2 995 66 6é
- aa 3 140 “é oa
es as 4 140 ae a
6é ¢é 5 120 6é 66
May 7 1 vA Off Tennessee Reef.
66 66 2 53 6e 66
66 ce 3 85 66 66
6é 6é 4 108 66 66
ée 66 5 114 66 66
66é ¢é 6 115 66 rz 4
es iy 7 124 vhs oa
as a 8 160 ue be
6c ce 9 174 66 sé
a se 10 200 «4 bi
ee 8 2 41 Off Alligator Reef.
6 sé 3 53 ‘a4 74
é¢ 66 4 68 66 6é
* 5 79 Gs “6
6é 6¢ 6 88 éé ee
es Gs 7 110 “ af
66 (79 8 110 6é 66
6 BULLETIN OF THE
1869. No. of Dredging. Fms. Locality.
May 8 9 ' 113 Off Alligator Reef.
sé 66 10 118 66 3
“cc RGei ilk 138 66 66
‘6 “cc 12 147 66 T3
é ‘6 13 156 66 rT;
TL 14 189 “ “
ie 15 238 « z
anny 3 | 1 30 Off Conch Reef.
66 66 2 39 66 66
sé 66 3 49 66 66
66 6c 4 60 66 66
&é 66 5 Yh 66 6¢
sc se 6 1 by / 66 66
sé 6 7 139 66é ce
sc 66 8 157 66 66
bc 3 9 169 6< <3
“6 66 10 957 3 6c
Eo ae 1 30 Off Pacific Reef.
és éé 2 49 6s 66
«sé eé 3 60 66 66
6 “ 4 75 Te rT
66 6 5 98 ‘6 6c
« és 6 180 ; “ ‘c
66 66 7 233 rT; 66
66 66 8 283 66 66
6¢ 66 9 987 66 66
The following dredging stations were occupied by the U. S. Coast
Survey steamer “ Hassler,” Lieut.-Commander P. R. Johnson, U.S. N.,
commanding, during her voyage from Boston to San Francisco, in 1871
and 1872. Prof. L. Agassiz was in charge of the scientific department ;
the dredgings were made by L. F. Pourtales, Assist. U. 8. Coast Survey.
No. of
1871. Dredging. ° Fms. Locality.
Dec. 29 1-4 75-100 Off Sandy Bay, Barbados.
a) -90 5-8 17-100 “6 as
1872.
Jan. 18 9 15 Lat. 11° 49’ S., between the meridians
ae a 10 17 of 37° 10’ and 37° 27’ W., standing
“6 “6 11 40 off and on shore.
(74 é 19 500 6c 6é <6
“é 46 13 20 “é 6c¢ éé
«é 6 14 75D (74 6é 66
sé ac 15 200 66 66 66
MUSEUM OF COMPARATIVE ZOOLOGY. Wi
No. of
1872. ae al Fms.
Jan. 20 16 30
‘cc ‘é 17 20
73 sc 18 26
66 éé 19 44
As 22 20 35
‘6 rT 91 45
Feb. 20 22 70
‘6 ss 23 70
‘6 22 24 19
as 29 25 7
March 1 26 44
6s 3 27 30
“ec 4 98 1
6é 66 99 95
“ 7 30 30
a 9 31 55
66 TI 82 57
6¢ 12 33 58
66 13 34 22
ag 19 35 13
ee 20 36
6 al 37
- 27 38 135
April 16 39 7-9
ee 25 40 35
66 66 Al 64
66 66 42 66
66 “< 43 84
” a7 44 2410
ne 29 45 656
ws - 46 1144
May 2 47 65
66 ds 48 220
bi 13 49 45
Locality.
Off the Abrolhos, Brazil.
6s 66 66
66 66 6é
66 66 66
Off Cape Frio, Brazil.
66 66 66
Lat. 32° 0’ S., Long. 50° 15’ W.
6é 66 “eé
pant 34° 55’ S., Long. 54° 12’ W.,
off La Plata River.
aos 35° 12/ §., Long. 55° 30’ W.,
in La Plata River.
Lat. 37° 42’ S., Long. 56° 20’ W.
By O39! ¢¢ 960° 35!
cae baw Wi merrGa” sas
vee? og ee. 63° 50!
wm 8 ie tr 63> (hae
6 44°52! Ae 64° "10%
oe. £9? 264 40/5) 66° BO"
$69 FO SG" Ce DS 3 Naie
Off Cape Possession, Patagonia.
Anchorage at Sandy Point.
is at Port Famine.
& at Port Gallant.
Between Sholl Harbor and Cape
Tamar, Straits of Magellan.
Talcahuano Bay.
Off Talcahuano Bay.
Surface temp., 57.5°. Bottom
temp., 35°. Dredge lost.
Two miles off Cumberland Bay, Juan
Fernandez. Bottom temp., 39°.
Three miles N. W. of Juan Fernan-
dez. Bottom temperature, 36°.
Off Cumberland Bay.
66 66
Off Valparaiso.
"s 35° 29/ S., Long. 75° 11/ W.
During the season of 1877 and 1878 the dredging operations from
December to March were in charge of Alexander Agassiz, and the follow-
8
BULLETIN OF THE
ing stations were occupied by the U. 8. Coast Survey steamer “ Blake,”
Lieut.-Comm. C. D. Sigsbee, U.S. N., commanding. The cruise ex-
tended from Key West to Havana, from Havana westward along the
north coast of Cuba, from Key West to the Tortugas, thence to the
northern extremity of the Yucatan Bank and Alacran Reef, to Cape
Catoche and across to Cape San Antonio, returning to Key West, and
from Key West to the Tortugas, and northward to the mouth of the
Mississippi River.
1877-78.
Temperature.
Surface. Bottom. Locality.
73° 393° Off Morro Light.
77 ~=—-339$ = vi he
783 393 a, as (Bottom, soft coral ooze.)
774 39} 66 ‘6 66 sé
76 494 Lat. 24° 15’ N., Long. 82° 13’ W. (Soft coral ooze.)
Liat.'24° 17’ 80” N., Long. 82° 9’ W.
7&8 (Only mud brought up.)
Stat. Fms.
7. 801
2 805
8 924
4 936
229
5 152
6 137
9 ID
10. <ifz
11 37
12 36
18 742
850
14 900
15 785
16 292
17 320
18 756
19 310
20 220
21 287
22. ‘100
23 190
24. 342
25 635
26 110
27 392
28 863
29 955
30 968
70
77
76
76
76
76
77
77
78
78
72
73
75
554
404
441
394
394
394
Seven m. 8. by W. from Sand Key.
Lat. 24° 44’ N., Long.:83° 26’ W.
Lat. 24° 43’ N., Long. 83° 25’ W.
Lat. 24° 34’ N., Long. 83° 16’ W.
Off Morro Light.
Lat. 23° 18’ N., Long. 82° 21’ W.
Near Morro Light, Lat. 23° 14’ N., Long. 82° 25’ W.
Near Morro Light, Lat. 23° 11’ N., Long. 82° 23’ W.
About 2 m. from Mariel, Lat. 23° 4’ N., Long. 82°
43’ W.
Off Mariel, Lat. 23° 7’ N., Long. 82° 43’ 30” W.
Off Bahia Honda, Cuba, Lat. 23° 3’ N., Long. 83°
10’ 30” W.
Off Bahia Honda, Lat. 23° 2’ 30” N., Long. 83° 11’ W.
he rg Lat. .23° 2’ N., Long. 83° 13" W.
as a Lat. 23° 1’ N., Long. 83° 14°.
a sh Lat. 23° 1’ N., Long. 83° 14’ W.
i a Lat. 23° 2’ 30” N., Long. 83° 13’ W.
a a Lat. 23° 4’ N., Long. 83° 12’ 30” W.
Lat. 24° 372’ N., Long. 83° 36’ W.
Lat. 24° 30’ N., Long. 83° 49’ W.
Lat. 24° 34’ N., Long. 84° 0’ W.
Lat. 24° 36’ N., Long. 84° 5’ W.
Lat. 24° 33’ N., Long. 84° 34’ W.
MUSEUM OF COMPARATIVE ZOOLOGY. )
Temperature.
Stat. Fms. Surface. Bottom. Locality.
a1 1920 394° Lat. 24° 33’ N., Long. 84° 23’ W.
32 95 . Lat, 23° 32’ N., Long. 88° 5! W.
1568-— ‘
83 400. 723°«40~— Lat. 24° 1’ N., Long. 88° 58’ W.
$4 syn «SSL 40 Lat. 28° 52’ N., Long. 88° 56’ W.
35 804 78 40} Lat. 23° 52’ 'N., Long. 88° 58’ W.
36 84 74. 60 Lat. 23° 13’ 'N., Long. 89° 16’ W.
37 35 N. W. end of Alacran Reef.
38 20 Yucatan Bank, Lat. 23° 10’ N., Long. 88° 35’ W.
39 14 Sixteen miles N. of Jolbos Islands.
40 1323 a7 40 Lat. 23° 26’ N., Long. 84° 2’ W.
41 860 73 93893 Lat. 23° 42/ N., Long. 88° 13/ W.
42 620 393 Lat. 23° 53’ N., Long. 83° 4’ 30” W.
43 339 45 Lat. 24° 8’ N., Long. 82° 51’ W.
44 539 7440-394 Lat. 25° 33’ 'N., Long. 84° 35’ W.
45 101 75 612 Lat. 25° 33’ N., Long. 84° 21’ W.
46 888 3935 Lat. 25° 43’ N., Long. 84° 47’ 30” W.
47 321 743 462 Lat. 28° 42’ N., Long. 88° 40’ W.
48 533 66 413 Lat. 28° 47’ 30” N., Long. 88° 41’ 30” W.
49 118 Lat. 28° 51’ 30” N., Long. 89° 1’ 30” W.
Stations 50 to 79 were occupied by Lieut.-Commander C. D. Sigs-
bee while in search of Pentacrinus.
Stat. Fms. Locality.
50 119 Lat. 26° 31’ N., Long. 85° 53’ W.
51 243-450 Off Havana, Lat. 22° 11’ N., Long. 82° 21’ W.
52 158 s ¢ Lat. .22° 9’ N., Long. 82° 23’ W.
53 242 7 si
54 175 ag ba
55 242 re ‘oy Lat. 22°: 9) N., Lone, 82° 21" W.
56 175 os ‘¢ Lat. 22° 9’ N., Long. 82° 21’ 30” W.
57 Aa i: me “¢ Lat. 22° 9’-15” N., Long. 82° 21’ W.
58 242 es ss Lat. 22° 9’ 30” N., Long. 82° 11’ 30” W.
59 158 Mig as
60 480 f sa
61 243 «© Lat, 22° 9’ N., Long. 82° 1’. W.
62 80 66 66
63 177 a6 as
64 122-240 ae S$
65 127 Be %
66 80-100 os “
10 BULLETIN OF THE
Stat. Fms. Locality.
67 128-240 Off Havana.
68 243-458 - be
69 100 ba in
70 111 Off Sand Key.
71 458 Off Havana.
72 50 Off Sand Key.
73 220 Lat. 23° 25’ N., Long. 83° 11’ W.
74 287 Lat. 23° 25’ N., Long. 88°.11' W,
75 292 Off Havana.
76 154 ag Oe
we 240 ee ae
78 129 66 6s
79 ges $3) Ss ‘6
During the season of 1878-79 the dredging operations, from Decem-
ber to March, were in charge of Alexander Agassiz, and the following
stations were occupied by the U. 8. Coast Survey steamer “ Blake,”
Commander J. R. Bartlett, U. S. N. The cruise extended from Key
West to Havana, from Havana to Jamaica through the Old Bahama
Channel and Windward Passage, from Jamaica to St. Thomas along the
south coast of Hayti and Porto Rico. From St. Thomas the “Blake”
visited Santa Cruz, Saba Bank, Montserrat, St. Kitts, Guadeloupe,
Dominica, Martinique, St. Lucia, St. Vincent, the Grenadines, Grenada,
and extended the dredgings south as far as the 100-fathom line off
Trinidad, returned to St. Vincent, and finished the dredging operations
at Barbados.
1878-79.
Temperature.
Stat. Fms. Surface. Bottom. Locality. Nature of Bottom.
250 “
100 400 Off Morro Light.
] 0 1 one 66 66
102 128 783° 69° Caya Cruz to Lobos Light. White coral sand.
103 438 79 49% Old Bahama Channel.
104 «4500 765 452 bi “s
105 452 77% 483 ne . Wh. coral sand, gritty.
106 2694 «“ “6 “ “fine.
107 428 2 ‘*
108 994 78 39 Off Nuevitas. Sticky yellow gray ooze,
very fine, & chalk rock.
109 1554 76 883 Off Cayo de Moa. Soft gray glob. ooze.
110 1205 78 883 Off Cape Maysi. Greenish black ooze.
Fms.
1200
1050
634
459
228
150
874
238
1105
1952
2393
2412
1450
580
300
226
38
180
314
451
18
580
115
42
248
450
508
625
2376
218
1097
861
27
150
21
270
245
MUSEUM OF COMPARATIVE ZOOLOGY. 11
Temperature.
Surface. Bottom. Locality. Nature of Bottom.
80° 394° Lat. 19° 7’ N., Long. 74°52’ W. Soft gray glob. ooze.
82 394 W. of Navassa Bank. Brown mud.
82 43 Off E. end of Jamaica. ee
Lat. 17° 54’N., Long. 76° 42’ W. *
Lat.17°55’ N., Long. 76°41’ 20” W. Dk. br. mud,very
Near former. [ soft.
824 40 Lat. 17° 47’ 20’ N., Long. 67° Gray gritty ooze.
3’ 20" W.
Lat. 18°12/ N., Long. 64°55’ W.,
between St. Thomas and San-
ta Cruz.
804 39 Same line. Grayish glob. ooze.
80 388 <“ & Grayish br. glob. oz.
80 394 a Gray glob. ooze.
774 382 oe ate be oe fo IN a. ‘“
Long. 64° 54’ 50” W.
803 382 Lat. 17° 49’ 15” N, Long. 64° Gray ooze and white
53 207 W. . coral sand, mixed.
81 42% Off Santa Cruz. F. wh. cor. and sil. s.
Near Ham’s Bluff.
79 503 Off Santa Cruz. Gray sand.
803 763 ae e Sand, blk. sp. & br. shs.
81 604 Off Frederickstadt, Santa Cruz. Gray ooze, sand.
85 48} - ee - ‘¢ Blue gray ooze, soft.
84 444 ie “ " *¢ Soft gray ooze.
79 77 Off Santa Cruz, Ham’s Bluff. Coarse corals. & shs.
81 423
tt. 65 as ‘* Frederickstadt. Rock and broken shs.
‘ ae Rock and broken shs,
81 544 _ ‘¢ Frederickstadt. Coarse s. and br. shs.
81 423 Ss Re a Sand and gray ooze.
80 424 “ el we Very soft gray ooze.
79h 414 o “4 i Fine gray ooze.
764 384 a es Very fine light br. oz.
784 51 ue ‘© Mt. Eacle. Fine sand & coarse gr.
80 384 Off Virgin Gorda.
784 404 sl “ Br. shells and oz.
784 77% Flannegan Passage. Sand and br. shells.
79 «©6634 ©6Off Saba Bank.
On “
795 51 Off St. Kitts. Fine sand, br. shells.
794 52 ss oh Very fine gr. sand, bl.
spk., ooze.
12
Stat.
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
a eB |
178
179
180
181
182
183
184
250
208
60
150
3734
356
122
303
298
Temperature.
Fms. Surface. Bottom.
794° 524°
794
79
794
804
554
76
45
674
483
BULLETIN OF THE
Locality.
Off St. Kitts.
66 66
6é 66
Between St. Kitts
and Nevis.
Off Nevis.
Off St. Kitts.
Off Montserrat.
66
6é
sé
Off Guadeloupe.
&é
¢é
66
Off Dominica.
Nature of Bottom.
Fine sand, blk. spk.
66 66
Fine ooze and lava spk.
Ooze and coarse fragments
of pumice. |
Lava sand, blk. spks., brk. sh.
Lava sand.
Stony bottom.
Rocky bottom, lava chips.
Lava sand.
€¢
Fine lava sand.
Came up empty.
Hard bottom.
Fine soft gray ooze, bl. sp.
Sand bl. spks. & br. shs.
Lost the trawl.
Lava sand and little oz.
Fine grayish-br. ooze.
Fine sticky br. ooze.
D. br. o. & s., brk. shs.
Fine sand & brk. shs.
Fine gr. s. with bl. sp.
Fine br. ooze & sand.
Fine brown ooze.
Fine br. ooze & sand.
Fine soft d. br. m. .
Fine sand, dark brown mud.
Stat.
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
MUSEUM OF COMPARATIVE ZOOLOGY. 93)
Temperature.
Fms. Surface. Bottom.
883. 80° 44°
98 80 66
411 794 43
372 80 43
84
os 79 693
542 791 42
oo 79 ~=664
250
138 75 638
169° 791 51
442 80 41}
5021 80 41
1030 80 39
1224. 80 $9
186 794 52}
196° 793 523
472 80 414
565 80 404
210 78 484
wo 2. G1
476 424
834 80 454
0, 79: .49
826 80 393
213 80 503
189 80 498
191
357
Bre RO! fot
357
892 793 394
226 fa -\) ‘Bt
154 794 54}
398 80 431
164 80 56
151 2 6 Dd
116 79 583
428 80 423
422 80 424
146 79 56
114 57
458 793 41}
Locality.
Off Dominica.
66
Off St. Vincent.
66
66
66
66
66
Nature of Bottom.
Fine sand, dark brown mud.
Fine sand, br. mud, and shells.
Fine sand, mud.
Fine sand, black mud.
66 66
Coarse sand, br. sh. fets., bl. m.
Fine sand, dark brown mud.
Fine sand, dark mud, & shells.
Fine sand, ooze.
Fine gray sand, and ooze.
66 66 66
Light brown ooze.
Rocky bottom.
Rocky bottom.
Hard bot., very little dk. br. s.
Fine dark gray ooze.
Coarse sand and broken shells.
Coarse sand and broken shells.
Fine sand, broken shells.
Fine sand and broken shells.
Fine s., yell. gr., very sticky.
Fine sand, brk. sh., ooze.
Hard bottom.
66 sé
Rough bottom.
Fine yellow sand and brk. sh.
Fine gray sand and ooze.
Sand and ooze.
Coarse sand and brk. shells.
Hard bottom, fine sand.
Rocky bottom.
Gray ooze.
Fine black sand.
Rocky bottom, coral.
Fine sand.
14 BULLETIN OF THE
Temperature.
Stat. Fms. Surface. Bottom. Locality. Nature of Bottom. iH
226 424 794° 423° Off St. Vincent. Fine sand, black sp., and ooze
227 573 80 403 ae ois Fine sand, gray ooze.
228 785 81 3894 me Very fine gray sand and ooze.
229 1004 79) 393 “die “ z «
20. 464. 1 Bigeere >
231 95 80 61} “ ts Coarse sand and rock.
232 838° 80. 62 =
238 174 80 49} peor abe Rocky bottom.
234 306 803 47 Off Bequia. Very rough, fine gray sand.
2385 1507 79 89 ¢ S Light brown ooze.
236 1591 79 39 os e Fine gray ooze.
237 1290 384 Off Grenadines. V. f. sticky oz., brownish gray.
238 127 79% 56 “ as Fine coral sand.
239 338 80 454 us “ Fine sand and ooze.
240 164 793 523 ae - Coral and broken shells.
241 163 80 53 TT |
242 842 80 393 rs + Fine sand and gray ooze.
“+ og il ED ee
244 792 72 89 Off Grenada. Gray ooze.
245. 1050. 7 39 i is Sticky fine br. blue ooze.
246 154 792 56 < as Fine gray ooze.
247 170 80 534 os me
248 161 80 533 “ a Fine gray ooze.
249 262 80 47 J es Coarse yellow sand.
250 421 80% 41} “ ae Coral sand and ooze.
251 382 80} 42 ‘* a Sand, little gray ooze.
252 306 80 444 Me Oe Gray ooze.
253 92 794 58% Hy ‘ Coral and broken shells.
254 164 78h 57 a - Coral and broken shells.
255 344 78 433 os od Dark gray ooze.
256 370 80 44% “ ss Fine sand and blue gr. ooze.
ang" 58:80 AOR ete
s58° "too 80° BoE es |
259 159 79k 53h“ «
260 291 794 47 us tf Fine gray ooze.
- 261 340 1:
262 92 80 62 a * Fine sand.
263 159 80 58h * &
94 AIG 80 «42, * “ Gray ooze.
265 576 795 392 = Kg
266 461 80$ 414 “ «
267 626 81 394 si “ Light brown and gray ooze.
268 955 80 393 os si Gray ooze, rocky bottom.
Stat.
269
270
271
272 -
273
, 274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
294
295
296
297
298
299
300
Fms.
124
75
458
76
103
209
218
94
106
69
118
221
288
154
237
347
13-
399
713
200
137
180
123
120
140
Temperature.
Surface. Bottom.
575° Off St. Vincent.
80°
MUSEUM OF COMPARATIVE ZOOLOGY. 15
66
41h
643
59%
53h
52k
44h
40
703
493
74h
644
544
503
614
564
61
564
60
sé
Locality.
66
Off Bequia.
Off Barbados.
66
ée¢
Nature of Bottom.
~
Fine sand.
Coarse sand & shells, hard bot.
Coral & broken shells, yellow.
Fine sand and ooze.
Fine sand, brown specks.
Hard rocky bottom.
Coral bottom.
Very rough, very rocky bot.
Glob. sand.
Glob. ooze and broken shells.
Coral sand and broken shells.
Hard bottom.
Fine s, glob. ooze.
Coral sand and broken shells.
Hard bottom.
Coarse coral s., broken shells.
Flat cale. stones.
Coral sand and broken shells.
66 66 66
Hard bottom.
Cale. stones.
Broken shells and coral.
Coral and corallines.
7 ay Gs _o sth. 4 yore das us Ta. oS. rar ahh eas ie
atl q se ad b k ae q Nay bi th
t cy. ‘ d ¥ ant ~ he) ih :
v™ re.) ‘* } ee a Way
: i Panter ine. : ;
i) ale y re P rt Mi
ra ie \ ‘ , :
ee Ps : - , : e a ne ‘ F ‘ :
aa! < |
ee te waliam nai lle La
= .. en .
- ‘S vey
tea ner ; vu saiichaak helt
NO EE a ee: per elisa dragged), |
ia ae Bi): Ga, ae Aegis wes Mita ae. |
pga, Te i ay . “ awe, sy
‘a (ie ‘ ‘ Haneunie oh lala Seed
ae re Dh ee ay
ee) oa ooo Na oy ie
= ; A id , “4, aie (poe i y
omg hogar aes ‘ Hey Dike
al ao a et ee ry a: Le - lupe Se
“ ; pe
e oa ae > hei east we, tae j ‘ ry d ; ry : ore? agains SM a
ey cig salve bara outa : sce wt ee ih ih eee
Me a oe. Shaye Aen? 4 “" HS hth Talal
— Ble Hite OSB.” * Oe: Oe
aan gael Licgs Awe TD: |) Os ae Een
a n 5) qv : "as A b fog: tt i . aa j Ping or Oe
RE iA eee ass eit oss NS
ey Meee HP ee oe ae
; A P . : ; . oe + ; 7 we hay ts‘ae .
eae Bae Be pate Byes oN ge ear
o. ae = 4 } te ? on. S > a
4 ae - U } he he i 7
M . f ‘ ' : ~*~
Oe . 7 ‘ 1 ¥ 7 -
ERR «EES SRE INE, Ai i
- ' tg ‘Av riaeth ale oil r An ese
emiee) Silvis) Wate te %, 20%) eM pda
aoe .; peas on Peer rhe
, tae x . . - s .
eo ‘ ; femal teas ‘1 - -
ea) A ba ‘ Ww
a ts i Ta j
F< soe a) ‘—@r
' iy yy ‘
i ; a
a AY! tes I] + - 4
te | A
af ‘ “Mint 1 a :
ru . oe 3 ;
ab, =
| oad 2° gle
*
A
i -* ses
1
i
*
*
No. 2.—Ophiuride and Astrophytide of the Exploring Voyage
of H. M. S. “ Challenger,’ under Pror. Sik WYVILLE THOMSON,
F.R.S. By THropore Lyman.
PART IT.
(Published by permission of the LorDs COMMISSIONERS OF THE. TREASURY.)
Turs concluding portion of the Prodrome contains the Ophiuride not
included in Part I, and the Astrophytide.
There are two new genera and sixty-three new species: Amphiura,
19 species ; Ophiocnida, 2; Amphilepis, 3; Ophiactis, 7; Ophiostigma,
1; Ophiopholis, 1; Ophiochondrus, 1; Ophioconis, 2; Ophiomyces, 2 ;
Pectinura, 2; Ophiopeza, 1; Ophiothrix, 4. Also of the genera already
treated, there have since been detected in Ophiochiton and Ophioglypha
one new species each ; and in Ophiacantha, four. Of Astrophytidee there
are, Astroclon, 1 species; Astrotoma, 1; Astroceras, 1; Astroschema, 5;
Ophiocreas, 4.
There is added an index of the species contained in the two parts, to-
gether with such other species from considerable depths as I have from
time to time described ; the whole forming a list of the greater portion
of the deep-sea Ophiurans and Astrophytons now known.
CAMBRIDGE, Mass., December 25, 1879.
VOL. VI. — NO. 2. 2
18 BULLETIN OF THE
Disk-scales swollen, humpvy, and irregu-
lar. ‘Ten stout, sharp arm-spines. Basal
mouth-papillze wide and scale-like. Ten-
jor scales very large, one overlapping the
other,
maxima.
Four straight, tapering
arm-spines. Disk-scales
delicate. Upper arm-plates
Radial shields | thin.
aero about } Radial shields smalland
ree times as nearly or quite separated.
:
j
long as wide. {Seven or eight
d
|
bellis.
blunt, crowded, thick ¢ ‘4%
arm-spines. Outer mouth-
papilla scale-like.
Radial shields very small, broad, about
twice as long as wide. Five or six short,
conical, barred spines. Upper arm-plates
narrow and rounded.
Radial shields broad, about twice as long
AMPHIURA.
TABLE OF SPECIES HEREIN DESCRIBED..
as wide. Three or four short, moderately
| Raat arm-spines. Tentacle-scale minute.
: Two tentacle-
scales.
Disk distinctly
scaled on both argentea,
| Radiat shields and upper arm-plates wider
4
—-——— >, a
acacia.
8
cale. ( Six short, stout arm-
spines. Disk- scales fine.
Radial shields | Upper arm-plates narrow.
narrow, about} our long, cylindrical )
thrice as long } arm-spines, the uppermost |
as wide. and lowest longest. Ten- | iris.
constricta,
tacle-scale large and
rounded.
Four tapering, equal arm-spines. ae
scales rather large and spaced. bed ha od
No tentacle-
scale.
Two (sometimes
: 2 . )
one) minute ten- Five slender, tapering arm-spines. Under
-ple ‘ i ield-shaped. Outer
tacle-scales. Ra- 2 °t™ plates squarish shie P + lanceolata,
dial shields long pee ah ep spiniform. Upper arm-plates
One _tentacle- than in A. Stimpsoni.
4
Two mouth-papille on each side. (O. mazima has a third rudimentary.)
Disk below en and narrow, :
or with rudimen- Five tapering arm-spines. Mouth-shields }
tary scales. One well-mark- | wide.
ed tentacle-scale. 1 Four or five tapering cylindrical arm-
spines. Mouth-shields rounded.
No _ tentacle- Radial shield pear-seed shape. Four to } dilkteam:
glatra,
} angularis.
scale. five small, widely-spaced arm-spines.
Th sath ill Two tentacle-scales. Fourarm-spines. Inner mouth-papillz
Tee mouth-papiile ? thick; two outer smalland sharp. Radial shields narrow and § concolor.
on each side.
separated.
Disk-scales fine; only
central primary plate con- dalee.
Three arm- | spicuous. First under
spines, the { arm-plate small.
middle one Disk-scales coarse; all
oe ese swelled. primary plates conspicu- ( ua,
i scale. ous. First under arm-plate
—, ap aa a j wide and large.
= co sgameapanea Four arm-spines. Disk naked below.
Tentacle-scale minute and like alip. Ra-
dial shields long and narrow, diverging
inward.
No tentacle-scale. Four arm-spines. Disk sealed on both
sides. Radial shields large, wide, and joined for half their
| length. Primary plates conspicuous.
Two tentacle-scales. Three middle mouth-papille longest. }
Point of mouth-angle occupied by lowest tooth.
One tentacle-scale. Mouth-papille squarish and crowded,
Side mouth-shields large and wide. Disk-scales irregular,
small, and crowded.
glauca.
Verrilli.
canescens.
on each side.
Five mouth-papillez
| patula.
MUSEUM OF COMPARATIVE ZOOLOGY. 19
Amphiura maxima sp. nov.
Plate XI. Figs. 278-281.
Special Marks. — Disk covered on both sides with swollen, lumpy, irregular
scales : ten stout, sharp arm-spines. Outer mouth-papille wide and scale-like.
Two very large tentacle-scales, one overlapping the other.
Description of an Individual (Station 188).— Diameter of disk 15 mm.
Length of arm about 135 mm. Width of arm, close to disk, without spines, 2.5
mm. One very large square mouth-papilla on each side of the angle, and a
pair much smaller and more rounded at the apex ; besides these, there may be
distinguished a minute papilla outside the great flat one. Mouth-shields large,
and much curved within, and prolonged by a rounded lobe without. Side
mouth-shields very small, pear-seed shape, with the smaller end inward ; they
occupy the inner lateral sides of the mouth-shield, and are widely separated.
Under arm-plates four-sided, broader than long, outer and inner edge slightly
curved, and with feeble re-entering curves on the lateral sides. Side arm-plates
short and high, scarcely prominent, meeting neither above nor below. Upper
arm-plates small, little swollen, nearly round ; but some distance out on the arm
they are broader than long. Disk round, flat, and rather thick, having a notch
over each arm ; surface covered above and below with rather large, rounded,
swollen, loosely overlapping scales, those in the interbrachial spaces being
slightly larger. Radial shields pear-seed shape, little swollen, with a peak in-
ward, separated their entire length by a row of three elongated scales, the inner
one being surrounded by several much smaller. On the outer edge of the radial
shields there is a row of small scales continuous with those on the margin of
the disk. There are ten stout, pointed arm-spines, the two lowest being about
twice as long as the others, much sharper, and usually curved. Two very large,
flat tentacle-scales with curved edges, one on the inner margin of the tentacle-
pore, which overlaps the one on the edge of the under arm-plate. Color in
alcohol, straw.
Station 188, 28 fathoms, 2 specimens.
Amphiura bellis sp. nov.
Special Marks. — Disk covered above and below with delicate scales ; two
tentacle-scales. Radial shields narrow, about three times as long as wide ; four
straight tapering arm-spines ; upper arm-plates thin.
Description of an Indwidual (Station 232). — Diameter of disk 7 mm. Arm
long, slender, and tapering gradually ; its width next the disk is 1mm. One
stout, short, blunt papilla on either side of the base of mouth-angle, and a pair,
stout and bluntly pointed, at its apex. The tentacle-scales of the first pair are
spiniform and rather conspicuous. Mouth-shields small and rounded, with
sometimes a rounded angle within and a slight lobe without. Side mouth-
shields three-sided, quite broad without, tapering within, where they do not
meet. First under arm-plate six-sided and rather larger than usual ; those
20 BULLETIN OF THE
beyond squarish, about as long as broad, with outer side nearly straight, lateral
sides a little re-enteringly curved, and usually a very short truncated angle
within. Side arm-plates small, and not strongly projecting, meeting neither
above nor below. Upper arm-plates thin, of a pretty regular transverse oval
shape, with lateral corners well rounded Disk rather thick, and slightly lobed,
covered above and below with small, rather thin, overlapping, scales, among
which the primaries are scarcely to be distinguished ; those near the margin
and underneath are finest, being 9 or 10 in 1 mm. long. Radial shields long,
narrow and pointed within ; length to breadth 2:.7; they are separated their
whole length by a narrow wedge composed of scales longer than those of the
neighboring disk. Four Ea stout, cylindrical, tapering arm-spines, of
equal lengths, and somewhat longer than the arm-joints. Two minute rounded
tentacle-scales, one on the side arm-plate, the other on the under arm-plate.
Color in alcohol, very pale brown.
‘The young of this species has sometimes only one tentacle-scale.
Station 232, 345 fathoms, 9 specimens. Station 174 (var. ?), 210-610 fath-
oms, | specimen.
Amphiura incana sp. nov.
Plate XI. Figs. 285-287.
Special Marks. — Disk scaled on both sides. Two tentacle-scales. Radial
shields narrow, about three times as long as wide, nearly or quite separated.
Lower scaling coarse. Seven or eight short, blunt, crowded, very thick arm-
spines.
Description of an Individual (Station, Simon’s Bay, Cape of Good Hope). —
Diameter of disk 7 mm. Arms about 70 mm. Jong, and slender ; close to disk
their width without spines is 1.3mm. One short wide curved papilla each side
of mouth-angle, and a pair, stout and bluntly pointed, at the apex of the mouth-
angle above ; the tentacle-scales of the first pair are conspicuous. Mouth-shields
small, of a wide diamond-shape, with outer angle truncated. Side mouth-shields
much longer than wide, tapering slightly within, where they nearly or quite meet ;
outer ends much rounded. Under arm-plates nearly square, with rounded cor-
ners, and outer edge a little re-enteringly curved. Side arm-plates rather thick
but not prominent, meeting neither above nor below. Upper arm-plates small,
narrow, squarish with rounded corners; narrow within, broader without. Disk
round, not very thick, covered with thin, very small overlapping scales: on
the upper surface there are 5 or 6 in the length of ! mm. Radial shields small,
of a long pear-seed shape, with outer edge rounded, separated their entire length
by a wedge of three rows of crowded, closely overlapping scales. Just outside
the radial shields there are numerous fine scales. On the under surface of disk
the scaling is much finer, there being about 12 in the length of amm. Eight
very short, stout, broad, nearly equal flattened arm-spines ; the two upper spines
are somewhat broader than the others. Two minute rounded tentacle-scales on
the side arm-plate. Color in alcohol, pale straw.
Station, Simon’s Bay, Cape of Good Hope, 10-20 fathoms, 12+ specimens.
MUSEUM. OF COMPARATIVE ZOOLOGY. 21
Amphiura argentea sp: nov.
Plate XI. Figs. 288-290.
Special Marks. — Disk scaled on both sides. One tentacle-scale. Radial
shields very small ; about twice as long as broad. Five or six short, conical
arm-spines. Upper arm-plates narrow and rounded.
Description of an Individual (Station 171).— Diameter of disk 4mm. Length |
“of arm about 22 mm. Width of arm near disk 1mm. One rather long, flat
papilla on either side'of the base of the small, short mouth-angle, and a pair,
much rounded, at apex. Scales of first pair of mouth-tentacles long and rather
conspicuous. Mouth-shields much wider than long, rounded, with a wide curve
within, and outer side feebly curved. Side mouth-shields very narrow within,
-where they meet ; wider without. First under arm-plate small and narrow,
being squeezed between the outer ends of the side mouth-shields ; those be-
yond are as broad as long, bounded without by a clean curve, on lateral sides
by slightly re-entering curves, and within by a truncated angle. Side arm-
plates very short, so that there is a considerable naked space between them on
the sides of the arm ; they stand well out, forming a strong spine-ridge. Upper
arm-plates narrow, donger than broad, nearly pentagonal, with rounded corners
and an angle inward. Disk delicate, covered above and below with minute,
thin, nearly uniform, overlapping scales; 9 or 10 in the length of 1 mm.
where they are smallest. Radial shields very small, slightly sunken, of a pear-
seed shape, nearly or quite touching without, separated within by a narrow
wedge of minute scales ; length to breadth .9:.3. Five or six short, nearly
equal, stout arm-spines, whereof the lower are cylindrical and tapering, and the
upper somewhat flattened and wider ; lengths to that of an under arm-plate,
.6, .6, .5, .6, .6, .7,.4. Near tip of arm there are three long, sharp, and very
slender spines, twice as long as the arm-joints: this so great variation of
form is rare in Amphiura. One oval tentacle-scale. Color in alcohol, nearly
white.
Station 171, 600 fathoms, 1 specimen.
Amphiura acacia sp. nov.
Plate XI. Figs. 292-294.
Special Marks. — Disk scaled on both sides. One minute tentacle-scale.
Three short, moderately stout arm-spines. Radial shields short and wide.
Description of an Individual (Station 235).— Diameter of disk 4.5mm. Length
of arm, about 32mm. Width ofarm neardisk, 1mm. One flat rounded papilla
on each side of the mouth-angle, and a pair, blunt and thicker, at the apex. Scales
of the first pair of mouth-tentacles flat, and low down, so as to seem nearly on
a level with the outer mouth-papilla. Mouth-shields small, rounded, longer
than broad, widest without, and having a rounded point inward. Side rhouth-
shields three-sided, short and broad, .widely separated within. Under arm-
plates narrow, longer than broad, five-sided, with an angle within, outer side
ae BULLETIN OF THE
nearly straight, and lateral sides a little re-enteringly curved. Side arm-plates
somewhat flaring, with a well-marked spine-ridge, meeting narrowly above and
barely separated below. Upper arm-plates twice as broad as long, with a clean
curve within and the outer side nearly straight, but having usually a feeble
lobe in the centre. Disk rather thick, covered with fine, curved, rather thin,
overlapping scales, which are largest in the centre, where may be distinguished
an ill-marked rosette of primary plates ; thase near the margin are much finer
(about 8 in the length of 1 mm.) : on the lower surface they become thinner and
near the mouth-shield are hard to distinguish. Radial shields short and wide,
curved on the interbrachial side, straight on the brachial ; barely touching
without, separated within by a narrow wedge of four or five scales ; length to
breadth, 1.1: .6. Three short, cylindrical, gently tapering, blunt, equal arm-
spines about .5 mm. long. One minute, rounded tentacle-scale. Color in alco-
hol, pale gray.
Station 235, 565 fathoms, 3 specimens.
Amphiura constricta sp. nov.
Plate XI. Figs. 295-298.
Special Marks. — Disk finely scaled on both sides. One tentacle-scale. Ra-
dial shield narrow, about thrice as long as wide. Six short, stout arm-spines.
Upper arm-plates narrow.
Description of an Individual (Station, Port Jackson).— Diameter of disk, 5mm.
Length of arm, 30mm. Width of arm near disk, 1 mm. One minute, rounded
papilla at base of mouth-angle, on either side, and a pair, much larger, at the
apex. Above may be seen the small scales of first mouth-tentacles, which resem-
ble the outer mouth-papille. Mouth-shields wider than long, of a three-sided
or wide heart-shape with rounded angles. Side mouth-shields long and narrow,
especially within, where they do not meet. First under arm-plate small and
very narrow ; those beyond are small and narrow, a little longer than wide, and
four-sided with rounded corners ; they cover only a small portion of the un-
der side of the arm. Side arm-plates small and not projecting. Upper arm-
plates small and covering only a portion of the upper side ; pretty regular
transverse oval, about twice as broad as long. Disk thick and somewhat
puffed, covered with regular, small, rounded, overlapping scales, which are
somewhat larger near the centre, where small round primary plates, widely
separated by smaller scales, may be distinguished ; below and near margin of
disk, the scaling is finer and more delicate, about 10 in the length of 1mm.
Radial shields long, narrow, and slightly curved, acute within, separated their
whole length by a wedge of many irregular scales of several sizes ; length to
breadth, 1:.3. Six small, short, stout, blunt, peg-like, equal arm-spines about:
.3mm., long, of which one or two are microscopically rough at theirends. The
spines at tip of arm are similar, but proportionately longer. One rather large
oval tentacle-scale.
Station, Port Jackson, Australia, 2 to 10 fathoms, 1 specimen.
MUSEUM OF COMPARATIVE ZOOLOGY. 2a
Amphiura iris sp. nov.
Plate XI. Figs. 302 - 304.
Special Marks. — Disk scaled above and helow ; one large oval tentacle-
scale: four long arm-spines, the uppermost and lowest longest.
Description of an Individual (Station 236).— Diameter of disk 5 mm.
Width of arm without spines 1.2mm. One short, stout, somewhat flattened
blunt papilla on each side of the mouth-angle, and a pair, similar, but some-
what smaller, at its apex. The large and broad scales of the first pair of tenta-
cles are low down and conspicuous. Mouth-shields of a very wide heart-shape,
much wider than long, with a rounded angle within. Side mouth-shields
thick, long triangular, tapering inward where they do not meet. First under
arm-plate usually large ; of a diamond shape, with its angles more or less trun-
cated ; the plates beyond are longer than wide, with outer side curved and
widest, lateral sides re-enteringly curved and a truncated angle within. Side
arm-plates stout and rather prominent, meeting neither above nor below.
Upper arm-plates fan-shaped, with inner angle more or less rounded, or trun-
eated, and outer side gently curved. Disk covered above and below, with mod-
erately coarse, crowded, irregular scales, those of the interbrachial spaces being
more elongated, and those on the under surface somewhat obscured by skin.
Toward the centre of the disk there are 7 or 8 scales in the length of 1 mm.
Radial shields much longer than wide, slightly curved, somewhat swollen,
tapering at both ends and widest in the middle ; separated their whole length
by a row of three or four large scales; length to breadth, 2:.6. Four long,
cylindrical, tapering arm-spines, whereof the uppermost and lowest are long-
est, and equal to 1% arm-joints. One large tentacle-scale. Color in alcohol,
pale gray.
Station 236, 420-775 fathoms, 1 specimen.
Amphiura tomentosa sp. nov.
Special Marks.— Disk scaled on both sides with rather large, spaced scales ;
those below somewhat obscured by thick skin ; four tapering, equal arm-spines ;
no tentacle-scale.
Description of an Individual (Station, Balfour Bay, Kerguelen Isl.).— Diam-
eter of disk 6.5 mm. Width of arm close to disk, without spines, 1mm. One
very small short mouth-papilla, often obscured by skin, on each side of the
mouth-angle, and a pair, larger and rounded, at the apex. Mouth-shields irregu-
lar, small, rounded triangular, with a small peak inward. Side mouth-shields
longer than broad, wider without than within, where they just meet ; both they
and the mouth-shields are somewhat obscured by skin. Under arm-plates
narrow, longer than broad, pentagonal, with a blunt angle inward, small re-
entering curves on the lateral sides, and outer lateral corners rounded. Side
24 BULLETIN OF THE
arm-plates moderately projecting, nearly meeting above and below. Upper
arm-plates somewhat broader than long, transverse oval, with a deep curve
within, and a gentler one without. Disk thick and round, covered with thin,
rather large, rounded scales, which are seldom overlapping, and often separated
from each other by much smaller ones. Radial shields small, quite narrow,
much wider without than within, where they form a sharp angle, widely sepa-
rated by a wedge of three or four scales. The interbrachial space on the under
surface is covered by fine scaling, which is often quite obscured near the mouth-
shields by skin. Four equal, rather long, stout, and blantly pointed arm-
spines.” Large round tentacle-pores, but no scales. Color in alcohol, pale
gray.
Station, Balfour Bay, Kerguelen Isl., 20-60 fathoms, 1 specimen.
Amphiura lanceolata sp. nov.
Plate XI. Figs. 305-307.
Special Marks. — Disk nearly or quite naked below. Two small tentacle-
scales. Radial shields long and narrow. Five slender, tapering arm-spines.
Upper arm-plates narrow. Under arm-plates squarish shield-shaped. Outer
mouth-papilla spiniform.
Description of an Individual (Station 169).— Diameter of disk 4mm. Arms
long and slender, about .7 mm. wide at the base. One slender, sharply pointed
mouth-papilla on each side of the mouth-angle, and a pair, short and much
rounded, at the apex. Mouth-shield small, thick, nearly oval. Side mouth-
shields three-sided, large and thick, as broad as long, curving round the inner
angles of the mouth-shield, but not meeting within. Under arm-plates nar-
row, longer than wide, pentagonal ‘in shape, with an obtuse, or truncated angle
inward, outer edge nearly straight, and re-entering curves on the lateral sides.
Side arm-plates not prominent, nearly meeting above and below. Upper arm-
plates much rounded triangular, with angle inward. Disk flat, with deep con-
strictions in the interbrachial spaces, The scaling of upper surface of disk is
rounded and overlapping, and is much coarser in the centre, where also the six
primary plates may be distinguished : near the margin there are from 8 to 10 scales
in the length of 1 mm. Radial shields long and narrow, sharply pointed within ;
joined without, where the ends are much rounded, and separated within by a
wedge of five or six scales. Interbrachial space on the under surface naked, or
with scattered, scarcely discernible scales. Five rather long, slender, cylindri-
cal, tapering, equal arm-spines about .6 mm. long. Two small rounded tentacle-
scales, one on the under arm-plate, and one on the side arm-plate. Color in
alcohol, pale gray.
Station 169, 700 fathoms, 1 specimen.
MUSEUM OF COMPARATIVE ZOOLOGY. 25
Amphiura glabra sp. nov.
Plate XI. Figs. 308 - 310.
Special Marks. — Disk below naked. Mouth-shields wider than long. Five
stout, tapering arm-spines. One tentacle-scale. .
¢ Description of an Individual (Station 214).— Diameter of disk 5mm. Length
of arm about 20 mm. Width of arm close to disk, without spines,.8mm. One
‘stout mouth-papilla in shape of an elongated cone on each side, and a pair,
thick and rounded, at the apex of the mouth-angle. Mouth-shields broader
than long, rudely triangular, with outer edges much rounded, and a small peak
within. Side mouth-shields small, longer than broad, wide without, tapering
inward, where they do not quite meet. Under arm-plates narrow, longer than
broad, squarish, with re-entering curves on the lateral sides, outer corners
rounded, and often an obtuse truncated angle within. Side arm-plates of mod-
erate size, and slightly flaring, meeting neither above nor below. Upper arm-
plates somewhat arched, rudely triangular, with outer edge rounded, and a blunt
angle within ; further out on the arm they become transverse oval. Disk flat
and lobed, covered above with thin, rather indistinct scales; those in the
centre coarser and more rounded; those in the interbrachial spaces narrower
and more closely overlapping. Radial shields short pear-seed shape, longer
than broad, separated their entire length by a narrow wedge-row of small
scales. Interbrachial spaces on the under surface naked. Five rather stout,
tapering arm-spines, somewhat longer than the arm-joints, placed close to-
gether on the side arm-plate. One rather large round tentacle-scale near the
inner angle of the under arm-plate. Color in alcohol, nearly white.
Station 214, 500 fathoms, 1 specimen.
This species is allied to A angularis, but has a finer build ; side arm-plates
less prominent ; side mouth-shields smaller, and radial shields shorter and
wider.
Amphiura angularis, sp. nov.
Special Marks. — Disk below naked, or with a few rudimentary scales. One
well-marked tentacle-scale. Four or five tapering cylindrical arm-spines.
Mouth-shields rounded.
Description of an Individual (Station 150).— Diameter of disk 9mm. Length
of arm 45 mm. Width of arm, without spines, close to disk, 1.2mm. One
long, tapering, pointed mouth-papilla on each side, and a pair, short, blunt, and
much rounded, at the apex of the mouth-angle. The tentacle-scale of the first
pair is large and spiniform. Mouth-shields rather large, nearly circular, with a
small peak within. Side mouth-shields large, three-sided, broad without, and
curving downward about the mouth-shield, narrow and separated within.
First under arm-plate very small and squarish ; those beyond are nearly square
26 BULLETIN OF THE
and rather narrow, with outer corners rounded, and slight re-entering curves
on the lateral sides. Side arm-plates wide, prominent, and much swollen along
the spine-crest ; separated below, nearly or quite meeting above. Upper arm-
plates transverse oval, much wider than long, with well-rounded lateral ends.
Disk flat and angular, covered above with coarse, rounded, overlapping scales,
the five primaries being but little larger than the other scales ; the scaling on
the interbrachial spaces is finer than in the central portion. Radial shields
much longer than broad, tapering towards each extremity, with the inner point
acute, separated their entire length by two or three rows of irregular scales ;
length to breadth 2:.7. The scales of the margin continue round the outer
end of the radial shields. Interbrachial space below only about one third
covered with minute scaling; the rest of the space is naked. Four stout,
blunt, tapering, cylindrical arm-spines, evenly spaced on the side arm-plate.
One stout, round tentacle-scale on the inner side of the tentacle-pore. Color in
alcohol, disk gray, arms straw.
Station 150, 150 fathoms, 12-+ specimens.
Amphiura dilatata sp. nov.
Plate XI. Figs. 314-316.
Special Marks. — Disk naked below. Radial shields narrow pear-seed shape.
Four or five small, widely spaced arm-spines. No tentacle-scales.
Description of an Individual (Station 141). — Diameter of disk 5mm. Length
of arm 23 mm. Width of same without spines, close to the disk,.7 mm. At
the base of the mouth-angle, on each side, is a long, very slender mouth-papilla,
and a pair, blunt and rounded, at the apex. Mouth-shield small, short diamond-
shape, with much rounded angles. Side mouth-shields small and curved,
narrow within, where they nearly or quite meet ; outer end wide club-shaped.
Under arm-plates narrow, longer than broad, squarish, with re-entering curves
on the lateral sides, and the outer edge nearly straight. Side arm-plates very
small, not prominent, nearly or quite meeting above, separated below. Upper
arm-plates transverse oval, with the inner curve stronger than the outer, and
the lateral corners pointed ; there is a slight longitudinal ridge. Disk rather
thick and slightly puffed; primary plates widely separated and scarcely to he
distinguished from the general scaling, which is fine, regular, and overlapping,
having about 10 scales in the length of 1 mm.; those of the interbrachial spaces
are smallest and most closely overlapping. Radial shields small, and slightly
swollen, narrow pear-seed shaped, separated their entire length by a narrow
wedge-row of scales ; a pair of short, stout scales at their outer ends. Under
surface of disk naked. Five short, tapering, blunt arm-spines, evenly spaced
on the side arm-plate, and standing at right angles to the arm; the middle
spine is stoutest. Large tentacle-pores, but no tentacle-scales. Color in alco-
hol, disk gray, arms straw.
Station 141, 98 fathoms, 12+ specimens.
MUSEUM OF COMPARATIVE ZOOLOGY. at
Amphiura concolor sp. nov.
Plate XII. Figs. 317-319.
Special Marks. —Three mouth-papille on each side, the inner one large and
thick, the two outer small and bead-like. Two, sometimes only one, small ten-
tacle-scales. Four arm-spines. Radial shields narrow and separated.
_ Description of an Individual (Station 195).— Diameter of disk 8mm. Length
of arm 65 mm. Width of arm close to disk, without spines, 1 mm. Two very
short, small mouth-papille each side of the mouth-angle, and a pair, large,
rounded, much swollen at its apex. Four large, thick teeth, with a square
cutting edge. Mouth-shield wide spear-head shaped, with a blunt angle within,
and the inner sides slightly curved. Side mouth-shields large, broad without,
tapering inward, where they just meet. Basal under arm-plates large, pentagonal
with the inner angle truncated, broader than long, outer edge straight, lateral
sides re-enteringly curved. Side arm-plates rather small, projecting moderately,
meeting neither above nor below. Upper arm-plates short and wide, of a trans-
verse pointed oval form, with outer and inner edge slightly curved. Disk
round and flat, but rather thick, covered with irregular, overlapping scales ;
those in the interbrachial spaces being somewhat coarser than the others.
Radial shields long and narrow, with outer end rounded, and an acute angle
inward, separated their entire length by a single row of scales. Interbrachial
spaces on the under surface covered by similar, but finer, scaling. Four short,
blunt, rather slender arm-spines, the upper one being slightly shortest. Two
small, rounded tentacle-scales, one on the brachial side of the tentacle-pore and
one on the side arm-plate. On some pores there is but a single scale. Color
in alcohol, straw.
Station 195, 1425 fathoms, 2 specimens. Station 191, 800 fathoms, 12+
specimens.
Amphiura dalea sp. nov.
Plate XII. Figs. 320 - 322.
Special Marks. — Four mouth-papillz on a side. Three arm-spines, the
middle one swollen. One tentacle-scale. Disk-scales fine, only the central
primary plate being conspicuous. First under arm-plate small.
Description of an Individual (Station 325).— Diameter of disk 9 mm.
Width of arm close to disk, without spines, 1.3mm. Three stout, close-set
papillee on either side of the mouth-angle, and two large and much rounded at
the apex ; of those on the sides the outermost is largest. Mouth-shields small,
triangular, a little longer than wide, rounded on all sides except within, where
isa point. Side mouth-shields large, broad without, tapering inward where
they just meet. First under arm-plate very small; those beyond are broader
than long, angular, and with re-entering curves on the sides where are the ten-
tacle-pores ; still farther out they are triangular, with outer edge much curved,
28 BULLETIN OF THE
and a truncated angle within. Side arm-plates short, not much projecting, meet-
ing above beyond the first upper arm-plate, and below beyond the seventh or
eighth. Upper arm-plates slightly swollen, very short and wide, of a trans-
verse oval shape, and with a small longitudinal ridge. Disk flat and tolerably
thick, covered with thin, small, flat, overlapping scales, with one somewhat
larger pounded primary in the centre ; about 4 scales in the length of 1 mm.
Radial shields long and broad, bluntly pointed within, nearly or quite sepa-
rated their entire length by a narrow wedge of scales. On the interbrachial
spaces on the under surface the scaling is much finer than.that above, there
being about 15 in the length of 1mm. Three tapering, rather sharp arm-
spines, the upper one being shorter than the other two, and the middle one
much the stoutest, and swollen. One small longer than broad tentacle-scale on
the brachial side of the tentacle-pore; a little way out on the arm there
usually is no tentacle-scale. Color in alcohol, pale straw.
Station 325, 2,650 fathoms, 5 specimens.
Amphiura cernua sp. nov.
Plate XII. Figs. 323 -325.
Special Marks. —Four mouth-papille on each side. One tentacle-scale.
Three arm-spines, the middle one swelled. Disk-scales coarse ; all primary
plates conspicuous. First under arm-plate wide and large.
Description of an Individual (Station 241).— Diameter of disk 5.7 mm.
Length of arm about 24 mm. Width close to disk, without spines .7 mm.
Four mouth-papille on each side, of which three are short and blunt (the inner
one being more pointed), and two at the apex of the mouth-angle are larger and
more swollen. Mouth-shields small, flat, triangular, with a blunt angle inward
and outer edge curved. Side mouth-shields broad without, and tapering inward,
where they just meet. Under arm-plates large, with a long angle within and
slight re-entering curves on tlie lateral sides. Side arm-plates slightly swollen,
meeting below some distance out on the arm, and above beyond the first upper
arm-plate. Upper arm-plates transverse oval, slightly swollen, with outer and
inner edges much curved. Disk flat and slightly angular, covered with thin,
semicircular, overlapping scales, the six primary plates being much the largest ;
the scaling in the interbrachial spaces is somewhat coarser than on the rest of
the disk. Radial shields very large and broad, somewhat longer than wide, of
a blunt pear-seed shape ; joined without, separated within by a wedge of two
small scales. On the under surface the interbrachial space is covered with
very minute scaling. One large tentacle-scale longer than broad. Three
short arm-spines, the upper one longest and slender, while the middle one
is strongly swollen at its base. Color in alcohol, straw.
Station 241, 2,300 fathoms, 1 specimen.
é
MUSEUM OF COMPARATIVE ZOOLOGY. 29
Amphiura glauca sp. nov.
Plate XII. Figs. 326 - 328.
Special Marks. — Four mouth-papillz on each side. One tentacle-scale mi-
nute and like a lip. Four slender arm-spines. Radial shields long and narrow,
and diverging inward. Disk naked below.
Description of an Individual (Station 232).—- Diameter of disk 5.5 mm,
Width of arm close to disk 1 mm. Four short pointed mouth papille on each
side of the mouth-angle, of which that at the apex is much the largest and
most rounded. Mouth-shield small, with a rounded angle inward, and outer
edge curved. Side mouth-shields small, long triangular, somewhat curved, just _
meeting within. Under arm-plates small, longer than wide, with re-entering
curves on the lateral sides, outer corners rounded and a truncated angle within.
Side arm-plates small and little projecting, meeting neither above nor below,
till some distance out on the arm. Upper arm-plates small, a little broader
than long, bounded within by a deep curve, and without by a gentler one, hav-
ing a small ridge in the centre, which forms a continuous line along the arm.
Disk rather thick, naked below, but covered above with very minute rounded
scales, about 7 in the length of 1 mm. where they are finest. Radial shields
long and very narrow, tapering inward te a blunt point; they are joined
without, and separated within by several small scales. Four slender tapering
arm-spines, the upper and under being usually somewhat longer than the two
in the middle. One very small lip-like tentacle-scale, on the inner side of
the tentacle-pore. Color in alcohol, dull gray.
Station 232, 340 fathoms, 4 specimens. Station 236, 420 fathoms, 1 date
men.
Amphiura Verrilli sp. nov.
Plate XII. Figs. 329-331.
Special Marks. — Four mouth-papille on each side. Four arm-spines. No
tentacle-scales. Radial shields lc rge and wide, and joined for half their length.
Description of an Individual (Station 54),— Diameter of disk 6 mm. Width
of arm, without spines, close to disk, 1 mm. Four short, blunt mouth-papille
on each side, the two at the apex being largest and conical ; between them may
be seen the lowest tooth, having a broken edge. Mouth-shields small, rounded,
with a slight angle within. Side mouth-shields large, narrow within, where
they meet ; broader without, where they curve partially round the mouth-shield.
First under arm-plate very small; those beyond are swollen, narrow, longer
than broad, having the outer edge much rounded, deep re-entering curves on
the lateral sides, and a short, straight side within. Side arm-plates small,
separated below, but just meeting above. Upper arm-plates much broader
than long, transverse oval, with the inner edge nearly straight, outer edge
curved, and blunt angles on the lateral sides. Disk flat, moderately thick and
30 BULLETIN OF THE
slightly angular, covered with small, thin, irregular, overlapping scales ; there
are six large, widely separated primary plates, one round one in the centre, sur-
rounded by five others broader than long. Radial shields large, longer than
wide, of an elongated pear-seed shape, their pointed inner ends being separated
by two small, angular scales. Interbrachial space on the under surface covered
by fine overlapping scales, smaller than those above. Four arm-spines standing
close together on the side arm-plates ; they are about as long as an arm-joint,
and rather slender and tapering, except the one next the lowest, which is
strongly swollen at the base. Large round pores, but no tentacle-scales.
Color, gray.
Station 54, 2650 fathoms, 1 specimen.
Amphiura canescens sp. nov.
Plate XII. Figs. 332 - 334.
Special Marks. — Five mouth-papille on each side, of which the three mid-
dle ones are longest ; point of mouth-angle occupied by the lowest tooth. Two
tentacle-scales. Three arm-spines about as long asa joint.
Description of an Individual (Station 171). — Diameter of disk 5mm. Arms
long and slender. Width of arm, close to disk, without spines, 1mm. Five
stout, blunt mouth-papille on either side of the mouth-angle, the three middle
ones being longer, broader, and more flattened than the rest. One large, tri-
angular papilla, or tooth, at apex of jaw. Mouth-shields broad triangular,
with blunt angles and outer edge much rounded. Side mouth-shields long
and narrow, but slightly swollen, broader without. than within, where they just
meet. First under arm-plate small, pentagonal, with an angle inward and
slight re-entering curves on the lateral sides ; the other basal plates are large,
with outer edge curved, and wider than the inner, and with lateral sides re-
enteringly curved. Side arm-plates not prominent, meeting neither above nor
below at the base of the arm. Upper arm-plates broader than long, transverse
oval, with lateral ends slightly pointed. Disk flat, but rather thick, its upper
surface covered with small, slightly swollen, irregularly shaped, overlapping
scales, about 5 in the length of 1 mm. where they are coarsest. Radial shields
blunt pear-seed shaped, slightly pointed within, separated by one large and
several small scales. Interbrachial spaces on the under surface covered by the
same kind of scaling. Three stout, tapering, bluntly pointed arm-spines, about
as long as a joint, the lowest slightly longer than the others, placed close to-
gether on the side arm-plate. Two tentacle-scales, the one on the ‘brachial
side small and narrow, the interbrachial one much larger, with wide, rounded
edge. Color in alcohol, nearly white.
Station 171, 600 fathoms, 2 specimens.
MUSEUM OF COMPARATIVE ZOOLOGY. 31
Amphiura patula sp. nov.
»Plate XII. Figs. 335-337.
Special Marks. — Five (sometimes only four) mouth-papille on each side.
One tentacle-scale. Mouth-papille squarish and crowded. Side mouth-shields
large and wide. Disk-scales small, irregular, and crowded. |
Description of an Individual (Station 156).— Diameter of disk 14.5 mm.
Width of arm close to disk, without spines,2 mm. Five (sometimes only four)
squarish, crowded mouth-papille on either side, whereof the outermost and
innermost are largest ; besides these there is an odd one at the centre of the
apex. Mouth-shields small, rounded triangular, with a blunt angle inward.
Side mouth-shields short and stout, rudely triangular in shape, the inner angles
not quite meeting at the apex of the mouth-shield. Under arm-plates pentag-
onal, with inner angle sometimes truncated, outer edge slightly rounded, and
small re-entering curves on the lateral sides. Side arm-plates narrow, bent, not
very prominent, meeting above, but just separated below. Upper arm-plates
much broader than long, transverse oval, with outer and inner edges gently
eurved. Disk flat, covered with thin, flat, irregular, crowded scales, among
which six small widely separated primary plates are with difficulty distinguish-
able. Radial shields large and broad, of a wide pear-seed shape, separated their
entire length by a narrow wedge of three or four scales. On the under surface
the scales are much finer and more rounded. Three short, round, bluntly
tapering arm-spines, the middle one larger than the others but not so Jong as
an arm-joint, and all placed low on the side arm-plate. Only one longer than
wide, somewhat swollen tentacle-scale, on the brachial side of the tentacle-pore.
Except that it has usually five, instead of four, mouth-papille on a side, this
Species stands related to A. dalea, from which it is distinguished by smaller
arm-spines, different under arm-plates, and coarser, more irregular scaling,
Color in alcohol, grayish.
Station 156, 1975 fathoms, 4 specimens.
Note. — The following are species previously known and now brought back by the ‘‘ Challenger,”
namely, A. sguamata, A capensis, A Otteri, A. duplicata, A. Studer (A. antarctica), A. depressa.
Amphiura capensis Ln.
Amphiura capensis. Of. Kong. Akad. Oph. Viv., 1866, p. 320.
Station 141, Lee’s Point, Cape Town, 98 fathoms, 12-++ specimens.
Amphiura duplicata Lym. /
Amphiura duplicata, Tl. Catal., No. VIII., Pt. 2, p. 19.
Station 56, 1,075 fathoms, 4 specimens.
Quite common in less depths throughout the West Indies. A. duplicata is
Sa BULLETIN OF THE
somewhat variable ; and, especially, the first under arm-plate is not always
broken in two. Numerous specimens from the second “ Blake” Expedition
show usually only three arm-spines; three and often four irregular mouth-
papille on each side, and disk-scales varying in thickness.
Amphiura squamata Sars.
Amphiura squamata. , Middelhav. Lit. Fauna, II., 1857, p. 84.
Station 141, 98 fathoms. Station 163, 120 fathoms, 1 specimen.
Such diverse localities further prove the cosmopolite nature of this species.
Amphiura Otteri? Lsn.
Amphiura Ottert ? Of. Kong. Akad. Dr. Goés, Oph., 1871, p. 631.
Station 76, 900 fathoms, 2 specimens. Station 45, 1,240 fathoms, 2 speci-
mens. Station 78, 1,000 fathoms, 1 specimen. Station 50, 1,250 fathoms, 1
specimen.
I have not much question that this is Ljungman’s A. Olteri which has some
variety as to size and curve of spines. The unique originals of this and many
other species were, with great kindness, lent me by Prof. Lovén; and Dr. G. O.
Sars showed a similar generosity.
Amphiura depressa ?
Amphipholis depressa Ljn. Of. Kong, Akad. Oph. Viv., 1866, p. 312.
Station 233, 15 fathoms, 1 specimen.
Amphiura Studeri.
Amphiura antaretica Studer. Monatsb. Kon. Akad. Wissen., Berlin, 1876,
p. 461.
Station 151, off Herd Isl., 75 fathoms, 1 specimen; var. Off Marion Isl,
50 -'75 fathoms, 10 specimens. Station 145, off Prince Edward’s Isl., 310 fath-
oms, 1 specimen (young). Off Prince Edward’s Isl., 85 — 150 fathoms, 1 speci-
men. Royal Sound, Kerguelen Isl., 28 fathoms, 12+ specimens. Balfour
Bay, Kerguelen Isl., 20 - 60 fathoms, 8 specimens.
As I have combined Amphipholis with Amphiura, Prof. Studer’s name has
become a duplicate to (Amphipholis) antarctica Lin. I take, therefore, the
liberty of giving it the name of its discoverer, who kindly identified these
specimens by his own.
Ophiocnida pilosa sp. nov.
Plate XII. Figs. 341-343.
Special Marks. — Disk scaling hidden. Disk set with stout simple spines.
Five tapering arm-spines, the lowest one longest. A slender mouth-papilla on
each side, and a pair of thick ones at apex of mouth-angle.
MUSEUM OF COMPARATIVE ZOOLOGY. 30
Description of an Individual (Station 162).— Diameter of disk 5.2 mm. Arm
broken, but apparently eight or ten times the diameter of disk. Width of arm
near disk 1.2mm. The short narrow mouth-angle has at its base on either side
a spiniform papilla, and at its apex a pair, stouter and more angular. Mouth-
shields longer than broad, nearly oval. Side mouth-shields triangular, some-
what curved round the mouth-shield, not meeting within. Under arm-plates
narrow, longer than broad, with eight sides, but having the angles rounded and
nearly obliterated ; lateral sides re-enteringly curved. Side arm-plates feeble,
nearly or quite meeting above, but not below. Upper arm-plates nearly twice
as wide as long, of a transverse oval shape, with inner curve deeper than outer.
Disk delicate but rather thick, sparsely set above and below with small spines ;
in the centre may be seen some round, very thin, primary plates ; the rest seems
naked, but on drying a very fine, delicate scaling appears. Radial shields much
longer than broad, slightly curved, meeting without, widely separated within ;
length to breadth 1:.5. Five cylindrical, tapering, blunt arm-spines, the
lowest somewhat the longest ; lengths to that of an under arm-plate, .5, .5, .5, .5,
.7:.5. No tentacle-scales. Color in alcohol, pale gray.
Station 162, 38 fathoms, 2 specimens. Station 212, 10-20 fathoms, 1 speci-
men.
Ophiocnida scabra sp. nov.
Plate XII. Figs. 344-346.
Special Marks. — Disk much puffed. Radial shields long and narrow. Five
or six short stout arm-spines, the second longest. Two minute mouth-papill
on either side, and a pair of larger ones at apex of mouth-angle.
Description of an Individual (Station 128).— Diameter of disk 6mm. Length
of arm about 40 mm. Width of arm near disk 1.3 mm. Two minute, bead-
like papillz on each side of base of small mouth-angle, and a pair, much larger,
at its apex. Mouth-shields small, rounded, about as broad as long. Side
mouth-shields small, bent, wider without than within, where they do not meet.
Under arm-plates as broad as long, bounded by a curve without, and within by
three sides of an octahedron. Side arm-plates narrow, widely separated above
and below, and having a feeble spine-ridge. Upper arm-plates two and a half
times as broad as long, of a clean, transverse oval shape. Disk extremely puffed
in the interbrachial spaces by the swollen ovaries. This swollen portion, both
above and below, is naked, and sparsely set with minute, peg-like spines ; but
above the surface is finely and pretty uniformly scaled, with about 6 scales
in the length of 1 mm. Radial shields long and very narrow, slightly bent
towards each other, nearly or quite separated their whole length by a narrow
strip of two scales ; length to breadth 1.5 :.3. Six short, thick, microscopically
thorny arm-spines, whereof the two uppermost are longest, somewhat flattened,
pointed, and have a minute beak ; those below diminish constantly in length,
and are almost club-shaped ; lengths to that of a lower arm-plate, .5, .7, .4, .3,
3, .2 : .3. One round tentacle-scale. Tentacles papillose, as in Ophiothriz.
Color in alcohol, pale yellowish-brown, mottled and speckled with darker.
VOL. VI. — NO. 2 8
34 BULLETIN OF THE
Station 128, off Bahia, Brazil, 1,275 fathoms, 1 specimen.
This eccentric species might almost as well go with Ophiactis.
AMPHILEPIS Lyn.
Amphilepis patens sp. nov.
Plate XII. Figs. 338-340.
Special Marks. — Disk flat, round and smooth. Mouth-angle large with
three wide mouth-papille on each side. Second pair of mouth-tentacles en-
circled by hard parts of the mouth.
Description of an Individual.— Diameter of disk, 11 mm. Width of arm
near disk, 2mm. Mouth-papillz broad and irregular ; on either side of the
large prominent mouth-angle, at the onter corner, are two more or less closely
joined ; and, at the apex, a larger pair which, through the gap between them,
show the small lowest: tooth. Mouth-shields rather small, rounded, broader
than long, often with a little peak inward ; length to breadth, 1:1.2. Side
mouth-shields short and wide; narrower within, where they barely meet.
Under arm-plates, rather small, as broad as long, shield-shaped, with a gently
curved outer side, lateral sides a little re-enteringly curved, and an obtuse
angle within. Side arm-plates wide, with a knob-like spine-crest, meeting
fully above and nearly or quite below. Upper arm-plates transverse oval,
twice as wide as long, separated by the side arm-plates. Disk round and flat,
but not thin ; covered above and below with rounded, overlapping, flat, rather
large, very thin, translucent scales, with indistinct outlines ; above they are of
pretty even size, except a marginal row of larger, each of which is .7 mm. long ;
below they are much finer; about 3in the length of 1 mm. Radial shields
large, of a rhomboidal form, except that the outer side is rectangular, much
longer than wide, strongly diverging, with the outer ends nearly touching, but
separated within by a broad wedge of numerous scales ; length to breadth,
3:1.2. Three stout, short, cylindrical, tapering, blunt arm-spines ; lengths to
that of an under arm-plate, 1.1, 1.2, 1.3 : .8. Tentacle-pores large, with one
minute scale on lateral side of under arm-plate. The roots of the second pair
of mouth-tentacles come low down, and thus seem framed by the surrounding
hard parts. Color in alcohol, pale gray.
Station 299, 2,160 fathoms, 1 specimen.
Amphilepis papyracea sp. nov.
Plate XVI. Figs. 429-431.
Special Marks. — Disk thin and flat, with thin, fine scales. Three tapering,
rather slender arm-spines, a little longer than an arm-joint. No tentacle-scale.
Radial shields nearly or quite separated their entire length.
Description of an Individual (Station 198).— Diameter of disk 9 mm.
MUSEUM OF COMPARATIVE ZOOLOGY. 35
Width of arm close to disk, without spines, 1.5 mm. Two wide, slender
pointed mouth-papille on each side, standing high up on the jaws. Four
teeth, the three upper ones flat and wide, with a curved cutting edge ; the
lowest thicker and more conical. Mouth-shields flat and small, of a wide
heart-shape with a rounded angle inward and outer edge rounded ; length to
breadth .7: 1. Side mouth-shields wide without, where they enclose the
corner of the mouth-shield, narrow and just meeting within. Under arm-
plates pentagonal with inner angle slightly truncated, lateral sides re-enteringly
curved, and outer edge straight. Side arm-plates with outer edge swollen ;
meeting above, and nearly so below. Upper arm-plates thin and translucent,
of a transverse oval shape, about twice as wide as long. Disk smooth, flat,
angular and very thin, covered with small, thin, rounded, ill-defined scales,
Radial shields with a vague outline, of a bent pear-seed shape, nearly touching
without, separated within by an oval of five scales ; length to breadth 2.5: 1.
Scaling on lower interbrachial space finer than that above. Three rather slender,
bluntly pointed, tapering, cylindrical arm-spines, a little longer than an arm-
joint, well up on the outer edge of side arm-plates. Tentacle-pores large, but
without a scale. Color in alcohol, pale gray.
Station 198, 2,150 fathoms, 1 specimen.
Amphilepis tenuis sp. nov.
Plate XVI. Figs. 432 -434.
Special Marks. —QOne minute tentacle-scale. One mouth-papilla on each
side.* Radial shields short and wide, and joined for half their length.
Description of an Individual (Station 237).— Diameter of disk 4 mm.
Width of arm close to disk, without spines, .7 mm. One wide, pointed, some-
what bent mouth-papilla high up on each side the mouth-angle, and a ‘pair,
short, thick, and rounded, at the apex. Mouth-shields small, twice as broad as
long, of a transverse diamond-shape, with rounded angles. Side mouth-shields
three-sided, short and swollen, wider without, tapering rapidly within, where
they scarcely meet. Under arm-plates broad pentagonal, with a short angle
within, outer side nearly straight, and laterals slightly curved. The first plate
is large and of a truncated wedge-form. Side arm-plates meeting broadly
above and nearly touching below. Upper arm-plates twice as broad as long, of
a nearly semicircular outline, with the curve inward. Disk flat and angular,
covered with very thin scales; in centre of the disk is a rosette of six large ill-
defined primary plates, each nearly surrounded by minute scales. Radial
shields short, wide pear-seed shaped, joined for the outer half of their length,
narrowly separated within by a wedge of small scales. Scaling on interbra-
chial space below, much finer than that above. Three short, cylindrical,
bluntly pointed arm-spines. One minute, rounded tentacle-scale, which easily
falls off. Color in alcohol, faint greenish-gray.
Station 237, 1,875 fathoms, 1 specimen.
* Sometimes broken in two, as in the figure.
36 BULLETIN OF THE
Amphilepis norvegica? Lun.
Amphilepis norvegica. Of. Kong. Akad. Oph. Viv., 1866, p. 322.
Station 45, 1240 fathoms, 1 specimen. Station 46, 1350 fathoms, 3 specimens,
So far as one may judge, without having a proper series, these are the adult
of Ljungman’s original. They have the disk as largeas9mm. ‘The radial
shields are pretty large and separated, and there is no tentacle-scale.
:
OPHIACTIS.
TABLE OF SPECIES HEREIN DESCRIBED.
Nore. — Following these descriptions will be found the species previously known and brought back
by the “‘ Challenger,” namely, O. asperula, O carnea, O. Savignyi, and O Miilleri.
Skin thick and much obscuring the scaling and mouth-shields. Radial shields narrow
and small, Five short, thick, blunt, flattened arm-spines.
} © resiliens.
Disk-scales distinct and naked, without’ spines. Three stout, blunt, tapering, cylin-
drical arm-spines. One large, flat mouth-papilla on each side. Teeth lobed. viel
arms.
Disk-scaling coarse, and with few or no spines. Three or four stout, blunt, tapering
arm-spines. Two or three mouth-papillz on each side. Teeth lobed.
Disk-secales coarse, and set with numerous short spines. Radial shields short and }
triangular. Four stout, cylindrical, tapering arm-spines. One mouth-papilla on each - O. nama,
side. Five arms. j
Disk finely scaled, and set with short, minute spines. Radial shields small and pear-
seed shaped. Four moderately stout, tapering arm-spines, the uppermost longest.} O. hirta.
Two or three minute mouth-papillz on each side. Seven arms.
Disk-scales coarse and thick, with large radial shields. No spines, except a few near
the margin. Four rather long and slender arm-spines, the upper one longest Two} O. poa-
mouth-papillze on each side.
Disk-scales larger in centre, where primary plates may be distinguished in a rosette.
No spines, or only an occasional minute one on the margin. Three or four rather long} O canotia.
and tapering arm-spines. Two mouth-papillze on each side.
O flexuosa.
O. cuspidata,
Of the above seven species, the first belongs with the shallow-water type of O. Savignyt; the rest
come under the type of O. Baili, whose species often inhabit the deep sea.
Ophiactis resiliens sp. nov.
Plate XIII. Figs. 362 - 364.
Special Marks. — Skin thick and much obscuring the scaling and mouth-
shields. Radial shields narrow and small. Five short, thick, blunt, flattened
arm-spines.
Description of an Individual (Port Jackson). — Diameter of disk 6.5 mm.
Length of arm 38 mm. Width of arm near disk 1.5mm. Mouth-angle very
small and short, carrying on either side two small, flat, squarish papille, and,
at its apex, a third, rounded, with a minute point like the teeth. Mouth-shields
small, of a transverse oval shape ; length to breadth .7: .5. Side mouth-shields
rather small and curved, broader without than within, where they meet.
Under arm-plates small and rounded, about as long as broad, having outer side
curved and inner side with ill-marked angles. Side arm-plates projecting in a
strong spine-ridge. Upper arm-plates flat, transverse oval in form, about twice
as broad as long. Disk covered below by a thick, naked skin, and above by
MUSEUM OF COMPARATIVE ZOOLOGY. 37
fine, crowded, irregular, thin scales, of the smallest of which there are about
5 in the length of 1 mm. Those near the radial shields are much larger ;
and there may be also obscurely distinguished six round primary plates, widely
separated by the fine scaling. The disk margin is beset with minute, sharp,
peg-like spines. Radial shields long and narrow, touching without, separated
within by a narrow wedge of about three scales; length to breadth 1.3: .4.
Five short, thick, blunt, flattened arm-spines, of which the uppermost is the
stoutest, but not longer than the rest. One oval tentacle-scale. Color in alco-
hol, above, olive green, mottled and banded with lighter ; below, yellowish
brown, with under arm-plates and arm-spines marked with orange.
Port Jackson, Australia, 30-35 fathoms, 1 specimen.
Ophiactis flexuosa sp. nov.
Plate XIII. Figs. 347-349.
Special Marks. — Disk-scales distinct and naked, without spines. Three
stout, blunt, tapering, cylindrical arm-spines. One large flat mouth-papilla on
each side. Teeth lobed. Five arms.
Description of an Individual (Station 171).— Diameter of disk 7mm. Length
of arm about 35mm. Width of arm near disk 2.3mm. Each side of the
short, narrow mouth-angle is occupied by a single very large, wide, flat: papilla,
while a third, standing under and resembling the teeth, is at the apex, and has
a rounded figure, with a decided peak or little lobe within. Mouth-shield
somewhat broader than long, of a rounded diamond-shape. Side mouth-shields
rather broad, wider without than within where they meet. First under arm-
plate small, and wider within than without; those beyond are narrow com-
pared with the width of the arm, much rounded, ofa short transverse oval
shape, with the inner side somewhat angular. Side arm-plates very wide,
meeting neither above nor below, and having but a feeble lateral projection.
Upper arm-plates broad and short, two and a half times as wide as long, of an
elongated transverse diamond-form, sometimes with outer side so straight as
nearly to be triangular. Disk without spines, and covered above with coarse,
rounded, thick, overlapping scales, of which there are four or five radiating rows
in the narrowest part of each interbrachial space. Below, the scales of the in-
terbrachial space are much finer (4 or 5 in the length of 1 mm.), and regularly
imbricated. Three short, stout, cylindrical, scarcely tapering arm-spines of
nearly equal length, and about as long as one anda half joints; the upper
spine stoutest. One large oval tentacle-scale. Color in alcohol, pale brown.
Station 171, 600 fathoms, 2 specimens. Station 142, 150 fathoms, 10 speci-
mens, young ?
The ten specimens from Station 142, 150 fathoms, may be the young of this
species. They have six arms, while O. flexuosa has but five, and are scarcely to
be distinguished from O. plana; and the question arises whether O. plana be
not a young animal. The so-called adult of O. Miilleri has five arms, and the
young six. F
38 “BULLETIN OF THE
.
Ophiactis cuspidata sp. nov.
Plate XIII. Figs. 359-361.
Special Marks. — Disk-scaling coarse, and with few or no spines. Three or
four stout, blunt, tapering arm-spines. Two or three mouth-papille on each
side. Teeth lobed.
Description of an Individual (Station 170).— Diameter of disk 5mm. Length
of arm 25mm. Width of arm close to disk 1.3mm. ‘Two large, broad, flat
mouth-papillz on each side, whereof the outer one is larger. Seven or eight
large flat teeth, of a very wide heart-shape, and having a little lobe, or peak,
within. Mouth-shields broader than long, wide heart-shape, or transverse
diamond-shape, with rounded angles ; length to breadth .6:.8. Side mouth-
shields stout, slightly curved, rather broad, meeting within, where they have a
rounded end. First under arm-plate stout and rather large, wider within than
without, and having re-enteringly curved lateral sides. The plates beyond are
shield-shaped, widest without, and having a somewhat obtuse angle within.
Outer side curved, lateral sides re-enteringly curved. Side arm-plates stout,
nearly meeting above and below, and having a well-marked spine-crest. Upper
arm-plates broader than long, of a wide, transverse diamond-shape, with the outer
angle much rounded. Disk thick and covered above with large, rather swollen
scales, whereof there are three lines in each interbrachial space ; in the centre
are six large, somewhat angular, primary plates, separated by single lines of
much smaller angular scales ; the lower interbrachial space is covered with fine,
thickened scales, from 5 to 8 in the length of 1mm. Radial shields blunt pear-
seed shape, swollen; nearly or quite separated by a wide wedge of two or three
scales. Along margin of disk are a few small, peg-like spines. Four stout,
smooth, tapering, regular arm-spines, the upper one longest ; lengths to that of
a lower arm-plate 1.7, 1.1, 1, .7 : .6. One stout, nearly oval tentacle-scale.
Color in alcohol, pale gray.
Station 170, 520 fathoms, 5 specimens. Station 171, 600 fathoms, 1 speci-
men.
Ophiactis nama sp. nov.
Plate XIII. Figs. 350-352.
Special Marks. — Disk-scales coarse, and set with numerous short spines.
Radial shields short and triangular. Four stout, cylindrical, tapering arm-
spines. One mouth-papilla on each side. Five arms.
Description of an Individual (Station 174). — Diameter of disk 6mm. Length
of arm about 45 mm. Width of arm near disk 2.2mm. One large, wide, flat
mouth-papilia at base of mouth-angle on each side, and one (which may be
called the lowest tooth) at the apex ; this last is broad and rounded, with a
minute peak within. Mouth-shields of a much rounded, transverse diamond-
shape; length to breadth 8: 1.1. Side mouth-shields stout, nearly meeting
MUSEUM OF COMPARATIVE ZOOLOGY. 39
without, broader without than within, where they touch. First under arm-
plate small and three-sided, wider within than without : those beyond are one
half broader than long, with a curved outer side, and an irregular, more or less
truncated angle within. Side arm-plates unusually wide, but not much pro-
jecting, nearly meeting above and below. Upper arm-plates much wider than
long, three-sided, with a faintly curved outer side, and an angle, sometimes trun-
cated, within. Disk plentifully set with short, slender, cylindrical spines, and
‘covered with well-rounded overlapping scales, which are large above (2 or 3 in
the length of 1 mm.), and more regular and much smaller below (4 or 5 in 1
mm.). Radial shields sunken, rudely triangular, short and wide, separated by
a broad wedge of three or four large scales; length to breadth 1.2:1. Four
cylindrical, tapering, blunt, rather stout arm-spines, the two upper ones largest
and somewhat longer than an arm-joint. One large, oval tentacle-scale. Color
in alcohol, pale straw.
Station 174, 210-610 fathoms, 1 specimen. Station 171, 600 fathoms, 1
specimen.
Ophiactis hirta sp. nov.
Plate XIII. Figs. 365-367.
Special Marks. — Disk finely scaled, and set with short, minute spines.
Radial shields small and pear-seed shaped. Four moderately stout tapering
arm-spines, the uppermost longest. Two or three minute mouth-papille on
each side. Seven arms.
Description of an Individual (Station 164%).— Diameter of disk 4.3 mm.
Length of arm about 14 mm. Width of arm near disk 1.2mm. Two or
three small, narrow, scale-like mouth-papille on either side of the very nar-
row mouth-angle ; and one, wide, flat, and pointed, at the apex ; this last may,
as in all similar cases, be considered the lowest tooth. Mouth-shields small, of a
much rounded diamond-shape ; sometimes nearly circular. Side mouth-shields
narrow, of nearly equal width, meeting within. Under arm-plates rather
small, as broad as long, bounded without by a strong curve, and within by
three sides of an octagon. Side arm-plates stout, projecting laterally in a well
marked spine-ridge, meeting neither above nor below. Upper arm-plates a
little broader than long, transverse oval, with the inner sides more or less
angular. Disk covered with coarse, thickened, irregular scales, those of the
under surface being sometimes wholly obscured by a thick skin ; those in the
centre are largest, but the primary plates are not readily distinguishable ; there
are small, peg-like spines scattered over the entire surface. There are seven
pairs of radial shields, which are small, sunken below the disk-surface, of a
blunt pear-seed shape, and separated by a rather wide wedge of three scales.
Four smooth, rounded, tapering, moderately stout arm-spines ; the upper one
longest; lengths to that of an under arm-plate, 1,.8, .7,.7:.5. One stout, oval
_tentacle-scale. Color in alcohol, gray mottled with pale brown.
Station 164%, 400 fathoms, 1 specimen.
40 BULLETIN OF THE
Ophiactis poa sp. nov.
Plate XIII. Figs. 356-358.
Special Marks. — Disk-scales coarse and thick, with large radial shields; no
spines except a few near the margin. Four rather long and slender arm-spines,
the upper one longest. 'Two mouth-papille on each side.
Description of an Individual (off Tristan d’Acunha).— Diameter of disk
5mm. Length of arm about 30mm. Width of arm near disk 1mm. On
each side of the short narrow mouth-angle are two rather large, squarish, flat
papille, of which the outer one is broader ; at the apex is usually a very small
heart-shaped papilla, similar in shape to the larger teeth above it. ‘Mouth-
shields much wider than long, of a rounded transverse heart-shape ; the inner
sides a little re-enteringly curved. Side mouth-shields of nearly equal width,
meeting broadly within. Under arm-plates wide shield-shaped, bounded
without by a broad curve, within by an obtuse or truncated angle, and on the
lateral sides by re-entering curves. Side arm-plates nearly meeting above and
below, not very wide, but projecting in a well-marked spine-crest. Upper
arm-plates broader than long, fan-shaped with an obtuse angle inward. Disk
covered with coarse, overlapping scales ; those below regular and smaller, about
4 in the length of 1 mm.; those above much larger and more irregular; in the
centre an irregular rosette of large, rounded plates, and in each interbrachial
space about three radiating rows of elongated scales. The disk margin is
sparsely set with small peg-like spines, Radial shields large, of an angular pear-
seed shape, separated wholly by a narrow wedge of two or three scales ; length
to breadth 1.5: 1. Four slender, cylindrical tapering arm-spines, the upper-
most longest ; lengths to that of an under arm-plate 1.2, .8, .8, .8 : .5. One
large, oval tentacle-scale. Color in alcohol, pale gray.
Off Tristan d’Acunha, 1,000 fathoms, 2 specimens. Off Tristan d’Acunha,
500 fathoms, 10 specimens. Both Station 135.
Ophiactis canotia sp. nov.
Plate XIII. Figs. 353-355.
Special Marks. — Disk-scales larger in centre, where primary plates may be
distinguished in a rosette ; no spines, or only an occasional minute one on the
margin. Three or four rather long and tapering arm-spines. Two mouth-pa-
pille on each side.
Description of an Individual (Station 73).— Diameter of disk 5.5 mm.
Length of arm about 17mm. Width of arm near disk 1.8mm. Two flat,
rather large, squarish mouth-papille on each side of the narrow mouth-angle,
and one at the apex, similar in form to the teeth, which are broad heart-shape
with a peak within. Mouth-shields wider than long, broad heart-shaped with
a rounded angle within, or wide transverse, rounded diamond-shaped. Side
mouth-shields rather narrow, of about equal width, meeting fully within. First
under arm-plate small and wider within than without ; those beyond are wide
shield-shaped, bounded without by a curve, on the lateral sides by re-entering
MUSEUM OF COMPARATIVE ZOOLOGY. 41
curves, and within by an obtuse or truncated angle. Side mouth-shields of
moderate width, nearly meeting above and below, and having a well-marked
spine-crest. Upperarm-plates broad, transverse diamond-shaped, with outer and
inner angles rounded. Disk covered with rather thick overlapping scales,
which are finest below, near the mouth-shields, where there are about 7 in the
length of 1 mm. Above, the centre is occupied by a rosette of two circles of
large rounded plates partially separated by a few small scales. Radial shields
‘short, wide pear-seed shaped, separated their entire length by a narrow wedge of
three scales. On interbrachial spaces below, a few minute, peg-like spines.
Four short, cylindrical, tapering, blunt arm-spines, all stout, especially the
lower ones ; upper spine longest, and about as long as one and a half joints,
One large oval tentacle-scale. Color in alcohol, pale straw.
Station 73, 1,000 fathoms, 2 specimens.
Ophiactis asperula Lrx.
Ophiactis asperula. Addit. ad Hist. Oph., Pt. II., 1859, p. 130.
Ophiactis magellanica Ljn. Of. Kong. Akad. Oph. Viv., 1866, p. 325.
Station 308, 175 fathoms, 1 specimen. Station 311, 245 fathoms, 1 specimen.
Station 312, 10-15 fathoms, 12+ specimens. Station 315, 5-12 fathoms, 7
specimens.
Ophiactis carnea Lun.
Ophiactis carnea. Of. Kong. Akad. Oph. Viv., 1866, p- 324.
Station, Simon’s Bay, Cape of Good Hope, 10-20 fathoms, 4 specimens.
Ophiactis Savignyi Ln.
Ophiactis Savignyi. Of. Kong. Akad. Oph. Viv., 1866, p. 323.
Station 208, 18 fathoms, 1 specimen. Zanzibar, 10 fathoms, 2 specimens.
Ophiactis Miilleri Lrx.
Ophiactis Miilleri. Vid. Meddel., Jan. 1856, p. 12.
Off Bahia, Brazil, 7-20 fathoms, 2 specimens, var. quinqueradia. Station
122, 350 fathoms, 2 specimens.
OPHIOSTIGMA Lrx.
Ophiostigma africanum.
Plate XIII. Figs. 368-370.
Special Marks.— Arms more than eight times the diameter of disk. Outer
mouth-papille very wide. Radial shields long, narrow, and joined.
Description of an Individual (Cape de Verde Isl.). -— Diameter of disk 2.2 mm.
42 BULLETIN OF THE
Length of arm 18 mm, Width of arm near disk.6mm. Three mouth-
papilla on each side of a mouth-angle, whereof the two inner ones are small,
short, and almost conical, while the outer is straight and very wide, extending
from the first under arm-plate about two thirds the length of an angle. Mouth-
shields three-sided, with rounded angles, bounded without by a curve, and
within by a rounded angle ; length to breadth, .2: .8. Side mouth-shields
wide, a little broader without than within, where they fully meet. Under
arm-plates small, pentagonal, with outer side nearly straight, lateral sides a
little re-enteringly curved, and an angle within. Side arm-plates nearly meet-
ing above and below, and having a thick, low, spine-crest. Upper arm-plates
small, irregular transverse oval, with the inner curve deeper than the outer.
Disk rather thick, standing nearly clear of the arms, as is usual in the genus :
covered with fine, thin, nearly equal, indistinct scales, whereof most are rounded,
but some, near the centre, are angular: there are about 12 in the length of
1mm. where they are finest. Along margin of disk are minute, peg-like,
scattered spines, which are not: jointed at the base. Radial shields long, nar-
row, and closely joined ; length to breadth, .6: .2. At their outer ends are
visible the points of the genital plates, in two little lobes. Three stout, equal,
peg-like, very short arm-spines, standing nearly at right angles with the arm.
Two minute, longer than broad tentacle-scales standing diagonally with the
arm-plate. Color in alcohol, nearly white.
St. Vincent, Cape de Verde Islands, 7 specimens.
O. africanum differs from O. isacanthum in having longer arms, and longer,
narrower radial shields ; and from O. formosa by its wide outer mouth-papilla
and longer arms.
OPHIOPHOLIS Mixt & TRoscu.
Ophiopholis japonica sp. nov.
Plate XIII. Figs. 374-36.
Special Marks. — Upper disk covered with thin scales and large radial shields,
neither of which have grains or spines, except the marginal scales. Five stout,
cylindrical, tapering arm-spines.
Description of an Individual (Station 236).— Diameter of disk 10 mm.
Length of arm about 40mm. Width of arm without spines near disk 2.7 mm.
Three or four small, irregular, flat, scale-like mouth-papille on each side, and
a flat clump of short, bead-like tooth-papillee at apex of mouth-angle. Mouth-
shields and side mouth-shields somewhat obscured by thick skin. The former
are transverse oval, much wider than long ; length to breadth .8:1.3. Side
mouth-shields small and short, with rounded ends, rather wider within
than without, and somewhat bent. Under arm-plates a little wider than
long, slightly separated, and with rounded corners. Side arm-plates closely
soldered with their neighbors, meeting neither above nor below, rising laterally
MUSEUM OF COMPARATIVE ZOOLOGY. 43
in astrong spine-ridge. Upper arm-plates transverse oval, twice as broad as
long, slightly swollen, each surrounded by a single line of rounded granules,
which are broader than long. Disk round and thick, with a flat top, covered
with thin, variously shaped scales, which, near the margin, are obscured by thick
skin; those of the centre small, round, and arranged in a rosette ; those farther
out, larger and elongated, arranged in three or four rows between the radial
shields in the interbrachial spaces, where they are beset with a few scattered
- grains, which at the margin become much more numerous and larger, and
appear as very short spines. Interbrachial spaces below covered with a few
grain-like spines. Radial shields large, pear-seed shaped, much longer than
wide, separated usually by a line of two large and two smiall scales. Genital
openings large and extending about two thirds the distance to the margin,
Five, rarely six, stout cylindrical, blunt, tapering arm-spines, whereof the second
and third are stoutest, and as long as one and a half arm-joints. One, and on
the first two joints sometimes two, small, rounded tentacle-scales. At tip of
arm are four slender spines, of which the lowest takes the form of a flat, long,
three-toothed hook, as elsewhere in this genus. Color in alcohol, above, light
pink ; below, pale straw.
Prof. P. Martin Duncan has recently published (Linnean Soc. Journ.
Zool., XIV. 460, 479) an Ophiuran, Ophiolepis mirabilis, of which he re-
marks: “This common species has the disk of Ophiolepis as diagnosed by
Miiller and Troschel, that is to say, the scales, which are of good size, and the
large radial shields, are environed by rows of small scales as by belts. But the
upper arm-plates have also the supplementary rows of small scales around them,
and there are also large accessory side pieces. Moreover, there are hooks on
the side arm-plates. This mixture of Ophiolepian and Ophiopholian characters
is very interesting ; and this species, I consider, renders the abolition of Ophio-
pholis as a genus inevitable.”
The meaning of this passage is not quite clear, because Miiller and Troschel
(Syst. d. Asterid., p. 89) diagnosed, not the whole genus, but only the first sec-
tion of it, as having belts of scales round the disk plates (e. g. 0. cincta). To
this section Ophiolepis has been restricted. The third section they described
as having spines on the scales. This last is Ophiopholis, a genus now rec-
ognized as quite remote from the true Ophiolepis, which stands nearer Ophio-
glypha, Pectinura, &c., while Ophiopholis approaches the Amphiure through
Ophiactis asperula. It is evident that Ophiolepis mirabilis is a true Ophiopholis,
lacking none of its characters, and standing quite near the typical O. aculeata.
The fact that certain small scales surround larger ones is not here of generic
importance, and probably results from the young stage of the specimen, which,
to judge from the figures, had a disk not exceeding 4 mm. in diameter. Ophio-
phos japonica differs from the old species as well as from O. mirabilis in its
more slender arm-spines, and in having the radial shields and much of the
upper disk free of grains or spines.
Station 235, 565 fathoms, 1 specimen. Station 236, 420-775 fathoms,
3 specimens,
44 BULLETIN OF THE
OPHIOCHONDRUS Lym.
Ophiochondrus stelliger.
Plate XIII. Figs. 371-3173.
Special Marks. — Disk finely and evenly granulated on both sides. Four
slender arm-spines, whereof the uppermost is much the longest.
Description of an Individual (Station 320), — Diameter of disk5mm. Length
of arm16mm. Width of arm near disk 1.3mm. Three mouth-papille on
each side, whereof the two outer are flattened and squarish, while the inner-
most is stout, rounded, tapering, and peg-like. Apex of mouth-angle occupied
by the lowest tooth, which sometimes is represented by two blunt, spiniform
papille similar to their next neighbor. Four rather narrow teeth, which
sometimes are almost spiniform, but usually are flattened. Mouth-shields
much wider than long, with a well-marked obtuse angle inward and the outer
side gently curved ; length to breadth,.7 : 1.1. Side mouth-shields long, rather
narrow, of nearly equal width, slightly curved, and fully meeting within. First
under arm-plate small, longer than broad, hexagonal, with rounded corners ;
the plates beyond are rather small, wider than long, bounded without by a
broad curve, and within by an obtuse angle ; the lateral sides are very short,
or are confounded in the outer curve. Side arm-plates small, somewhat wider
than long, fan-shaped, with inner angle rounded. Disk rather thick, finely and
uniformly granulated above and below, about 17 grains in the length of 1 mm.
Four cylindrical, tapering, rather slender arm-spines, whereof the uppermost is
longest : lengths to that of an arm-joint, 1.1, .6, .5,.4: .6. One small, narrow
tentacle-scale. Color in alcohol, straw.
Station 320, 600 fathoms, 7 specimens.
OPHIOCONIS Lrx.
Ophioconis antarctica sp. nov.
Plate XIV. Figs. 380-382.
Special Marks. — Seven slender, cylindrical, tapering arm-spines, the two
upper ones longest. One large tentacle-scale. Disk closely granulated, except
mouth-shield ; 5 or 6 grains in the length of 1 mm.
Description of an Individual (Station 150).— Diameter of disk 13 mm.
Length of arm about 60 mm. Width of arm at base, without spines, 2 mm.
There are to each angle of the mouth twelve or fourteen papille, of which the
innermost are slender and pointed, while the outer one on either side is broad
and squarish ; at the apex there is a cluster of four or five, which properly
might be called tooth-papille. Five or six rather narrow, flat, blunt teeth,
whereof the lowest is often split in two. Mouth-shields broad triangular, with
a blunt angle inward and outer edge nearly straight ; they are more or less
obscured by granules, which completely hide the side mouth-shields. These
MUSEUM OF COMPARATIVE ZOOLOGY. 45
are small, longer than wide, and broader without than within, where they
nearly or quite meet. Under arm-plates much broader than long, pentagonal,
with a blunt inner angle, outer edge slightly curved, and laterals re-enteringly
curved. Side arm-plates somewhat projecting, nearly meeting below, but well
separated above by the thick, broad, somewhat arched upper arm-plates, which
are wide fan-shaped, with a blunt angle inward. Under the microscope they
appear minutely tuberculous, while the lower plates are ornamented with wavy
‘lines. Disk thick and nearly round, completely covered with coarse, rounded
granules, 5 or 6in the length of 1 mm. on the upper surface, and more scattered
below. The underlying scales are extremely thin and smooth. Genital open-
ings long, extending from outer corners of mouth-shield nearly or quite to the
margin of disk. Seven long, smooth, cylindrical, tapering arm-spines, the two
upper ones as long as three or four arm-joints ; the others somewhat shorter.
One long, wide tentacle-scale, with a rounded point occupying the lateral side
of the under arm-plate. Color in alcohol, nearly white.
Station 150, 150 fathoms, 12-+- specimens. Off Prince Edward Isl., 85-150
fathoms, 12+; specimens. Off Marion Isl., 50-75 fathoms, 12-+ specimens.
Ophioconis pulverulenta sp. nov.
Special Marks. — Disk finely, closely, and evenly granulated, with about 14
grains in the length of 1mm. Eight or nine Jong, delicate, somewhat flattened
arm-spines, the three uppermost longest, and nearly equal. Two tentacle-
scales. |
Description of an Individual (Station 172).— Diameter of disk 12 mm.
Length of arm about 55mm. Width of arm close to disk, without spines,
3.2mm. Ten small, short, close-set, pointed mouth-papille on each side of
the mouth-angle, and one somewhat stouter at the apex ; the two outermost
are broadest and most rounded. Mouth-shields large, as broad as long, of a
rounded heart-shape. Side mouth-shields stout and wide, broader without
than within, where they do not meet. Both they and the mouth-shields are
more or less covered by a granulation, which, as well as that of the disk, is ©
liable to be rubbed off. Under arm-plates axe-shaped, much broader without,
where the edge is curved, and with deep re-entering curves on the lateral sides.
Side arm-plates thin and microscopically corrugated. Upper arm-plates thin,
with a central ridge, about twice as broad as long, much wider without than
within, with sharp outer lateral corners and straight sides. Disk round and quite
thick closely and evenly covered with minute granules, 12 or 14 in the length of
1mm. Underneath these granules there are fine uniform, overlapping scales,
about 5 in the length of 1 mm., among which the radial shields cannot be dis-
tinguished. Eight or nine long, slender, tapering, flattened arm-spines, whereof
the three uppermost are about 2.3 mm. long and nearly equal, and the other five
or six from 2 mm, to1.7 mm. long. Two long, thin, nearly oval tentacle-scales,
which are two thirds as long as an under arm-plate. Color in alcohol, pale
straw.
46 BULLETIN OF THE
Station 172, 240 fathoms, 1 specimen.
This species stands very close to O. miliaria of the West Indies, and comes
from a similar depth. It seems sufficiently distinguished by the arm-spines,
which are more numerous by one or two, and more flattened, showing even a
feeble tendency to become spatulate.
.
OPHIOMYCES Lym.
Ophiomyces grandis sp. nov.
Plate XIV. Figs. 383 - 385.
Special Marks. —¥Eleven sharp, flat arm-spines, set along the whole upper
and side edge of the plate, and growing longer from above down to the ninth.
Basal under arm-plates, large and squarish, and bearing three long spatula-like
tentacle-scales. - .
Description of an Individual (off Tristan d’Acunha).— Diameter of disk 6.5
mm. Length of arm about 25mm. Width of arm near disk 2.2mm. Four
or five broad, flat teeth, with a curved, cutting edge; the lowest one being
much the narrowest. Below these, and still on the jaw-plate, are three spini-
form tooth-papille. Then, from apex of mouth-angle, there radiate, on each
side, two rows of long, flattened mouth-papille, which completely hide the
underlying parts ; each row has five or six papille, of which the innermost one
is spiniform, resembling a tooth-papilla ; those beyond, more or less spatula-
shaped, grow progressively larger and wider, until the outermost has almost a
fan-shape ; all incline more or less downward and outward, so that they overlap,
tile fashion. On cutting away the mouth-papille, a small mouth-shield, of an
irregular, short diamond-shape, may be seen, together with small triangular
side mouth-shields, which nearly meet within. Length of mouth-shield to
breadth .7:.7. The jaws are long, narrow, and slender, with very large sockets
at their base for the second pair of mouth-tentacles. The first under arm-plate
is minute, triangular, and difficult to distinguish ; the second very narrow,
closely soldered with surrounding parts, and with deep re-entering curves on
the lateral sides ; the fourth plate is four-sided, about as broad as long, much
wider without than within, and with deep re-entering curves on the lateral
sides ; length to breadth .6:.7. Side arm-plates separated below, meeting
narrowly above, not swollen, but clean cut and flaring outward. Upper arm-
plates twice and a half as broad as long, shaped like segments of a circle, with
a clean curve outward ; near tip of arm they are nearly as long as wide, and
form a pointed curve, while the side arm-plates are but slightly flaring and
meet above on a line as long as the upper plate. The disk was much torn (as
usually is the case), but evidently was covered above and below with fine scales,
about 4 in the length of 1 mm., whereof many bore minute, peg-like spines.
Eleven arm-spines, increasing rapidly in length from the first to the ninth,
then diminishing ; the upper ones are slender, sharp, and little flattened ; the
lower ones are broad, flat, sharp, and shaped like a bronze sword ; lengths to
MUSEUM OF COMPARATIVE ZOOLOGY. AT
that of an under arm-plate, .2, .3, .3, .3, .5, .7, .8, 1, 1.2,.7,.7: .7. The basal
under arm-plates, as far as the fifth or sixth, bear on each lateral side three
long, flat, spatula-like tentacle-scales, which project over the pore; for some
distance beyond there are but two such scales, while a third, trowel-shaped,
stands on the edge of the side arm-plate. One third out on the arm there re-
mains only the large trowel-shaped scale. Color in alcohol, pale gray.
Station, off Tristan d’Acunha, 1000 fathoms, 2 specimens.
- The peculiar twisting upward of the arms and disk of Ophiomyces is explained
by the absence of radial shields, a want not yet observed in any other genus. It
seems, then, that one function of radial shields is to keep the disk in shape,
somewhat like the action of the sticks of an umbrella.
Ophiomyces spathifer.
Plate XIV. Figs. 386-388".
Special Marks. — Outer mouth-papille large and paddle-shaped. One flat,
rounded tentacle-scale. Ten flattened arm-spines of various shapes, whereof
the two lowest are borne on the under arm-plate.
Description of an Individual (Station 235).— Diameter of disk 3.5 mm.
Width of arm next disk 1.2mm. Three short, narrow, slightly flattened, peg-
like teeth, carried on a thick, lumpy jaw-plate, which also bears two long, flat,
narrow, spatula-like tooth-papille. On either side of the mouth-angle are two
radiating rows, each of about six long, flattened papille, which are imbricated
and point downward and outward, so that the entire mouth-angle is hidden by
them ; the inner ones are narrow and spatula-like, but outwards they grow
rapidly larger, so that the outermost are wide paddle-shaped, or even fan-shaped,
their length to extreme breadth being.7: .5. Mouth-shields shaped like a long,
sharp, narrow lance-head. Side mouth-shields three-sided, delicate, separated
as by a wedge by the mouth-shield, which extends inward considerably beyond
them. Within, and indistinctly separated from the side mouth-shields, project
the long jaws. These parts are all hidden, and can be seen only by cutting away
the mouth-papillz. Under arm-plates small, with re-enteringly curved lateral
sides, wider without, where they area little swollen, than within, separated by
the side arm-plates, which meet narrowly both above and below, and are highest
and most flaring at their outer edge. Upper arm-plates minute (sometimes
apparently wanting), twice as long as broad, and appearing like little swellings
just outside the juncture of the side arm-plates. The larger part of upper sur-
face of arm is thus left uncovered, so that the arm-bones and their muscular
bundles may be seen. Disk (as usual in the genus) distorted and pushed up-
ward, covered uniformly with minute, thin, translucent, flat scales, without
spines; there are about 13 inthe length of 1mm. Ten arm-spines, of which the
three highest are equal, slender, narrow and tapering, and as long as any; the
next two are of about the same length, but broad and flat, with rounded ends ;
the next three similar, but shorter ; the two lowest spatula-like, with ends cut
Square off, and carried, not on the side arm-plate, but widely spaced on the
48 BULLETIN OF THE
outer part of the under arm-plate ; lengths to that of an arm-joint, .5, .5, .5, .5,
.5, .4, .4, .3, .8,.3 : .5. One flat, short, wide tentacle-scale, broader without
than within, and, like many of the arm-spines and mouth-papille, microscopi-
cally striated. Color in alcohol, disk, gray ; arms, straw.
Station 235, 565 fathoms, 3 specimens in bad condition.
PECTINURA Forses.
Pectinura arenosa sp. nov.
Plate XIV. Figs. 392-394.
Special Marks. — Nine to eleven short arm-spines. Disk uniformly granu-
lated, with about 8 grains in 1 mm. long. No water-pores between under
arm-plates.
Description of an Individual (Station 162).— Diameter of disk 10 mm.
Length of arm about 42mm. Width of arm close to disk2mm. Fifteen
short, stout, pointed, crowded mouth-papille, the three outermost being some-
what the widest. Mouth-shields rounded triangular, about as broad as long,
with a blunt angle inward and outer side straight. Supplementary shield
semicircular, and about two thirds as large as the true shield. Side mouth-
shields very small, and short, occupying part of the outer angles of mouth-
shield, and widely separated within. First under arm-plate wide and large,
and nearly semicircular though the inner side is not quite straight ; those be-
yond are as broad as long. There are no water-pores between the plates.
Side arm-plates flat and not swollen, separated above and below. Upper arm-
plates short rounded oval; somewhat broader than long. Disk somewhat
angular and slightly swollen, closely covered above and below, except the
mouth-shields and side mouth-shields, with a fine granulation, about 8 grains in
the length of 1 mm. Genital openings extending from mouth-shield about
two thirds the distance to the margin. Nine to eleven short, stout, somewhat
flattened peg-like arm-spines, all about half as long as the side arm-plate, except
the lowest, which equals it. Two small rounded tentacle-scales on the side
arm-plate, whereof that on the interbrachial side overlaps the base of the lowest
arm-spines. Color in alcohol, disk pale yellowish brown, above ; arms darker,
with irregular belts of black and yellowish brown.
Station 162, 38 fathoms, 6 specimens. This species stands between P. spinosa
and P. infernalis.
Pectinura heros sp. nov.
Plate XIV. Figs. 389-391.
Special Marks. — Three very short arm-spines, low down on the side arm-
plate. No pores between lower arm-plates.
Description of an Individual (Station 191).— Diameter of disk 22 mm.
Length of arm about 100 mm. Width of arm close to disk without spines
MUSEUM OF COMPARATIVE ZOOLOGY. 49
4mm. Fifteen small, close-set mouth-papille to each angle, whereof the two
or three outer ones on each side are flat, rounded, and larger than the rest,
which are pointed ; there are two just under the teeth, and sometimes two
supplementary below and outside these. Mouth-shields long heart-shaped, with
a rounded angle within ; length to breadth 3: 2.2. Sometimes a rudimentary
supplementary piece may be seen, just outside. Side mouth-shields three-
cornered and small, oceupying only the outer corners of the mouth-shield.
Under arm-plates about as wide as long, bounded without by a curve, within
by a truncated angle, and laterally by re-entering curves. Side arm-plates
short, with rounded edges, meeting neither above nor below. Upper arm-
plates broad, highly arched, closely overlapping, with outer and inner edges
nearly straight. Disk flat and angular, closely and evenly covered with very
fine granules, 7 or 8 in the length of 1 mm., except the radial shields and one or
more plates along the margin. “Radial shields egg-shaped, longer than broad,
with outer and inner ends much rounded ; length to breadth 3.7:2. Lower
interbrachial space covered by same granulation as above, extending even to
the mouth-angle, but not on mouth-shields. Genital opening long, extending
from mouth-shield to margin of disk. Three short, small, blunt arm-spines
standing low on the side arm-plate, and about half as long as a joint. One
round tentacle-scale. Color in alcohol white.
Station 191, 800 fathoms, 1 specimen.
This species stands as near P. stellata as to any ; there are, however, no pores
between the under arm-plates, and but three short arm-spines. The only oc-
casional presence of rudimentary supplementary mouth-shields points once
more to the very close connection between Ophiopeza and Pectinura.
Pectinura maculata Vit.
Pectinura maculata. Proc. Bost. Soc. N. H., XII., 1869, p. 388.
Queen Charlotte’s Sound, New Zealand, 10 fathoms, 5 specimens.
Pectinura rigida Lym.
Pectinura rigida. Bull. Mus. Comp. Zool., I11. 10, 1874, p. 224.
Fiji Islands, 2 specimens.
Pectinura stellata Lrx.
Pectinura stellata. Addit. ad Hist. Oph., Pt. III., 1869, p. 33.
Station 208, 18 fathoms, 1 specimen,
Pectinura gorgonia Lrr.
Pectinura gorgonia. Addit. ad Hist. Oph., Pt. III., 1869, p. 33.
Fiji Islands, 1 specimen.
VOL. VI. NO. 2. 4
50 BULLETIN OF THE
OPHIOPEZA PETERS.
Ophiopeza aster sp. nov.
Plate XIV. Figs 395-397.
Special Marks. — Disk densely and finely granulated above and below, in-
cluding the mouth-angle.
Description of an Individual (Station 142).— Diameter of disk, 11 mm,
Length of arm, 33mm. Width of arm close to disk, 2mm, Teeth narrow,
sharp and lanceolate ; the two lowest usually split in two. The apex is occu-
pied by a bunch of three or four short, crowded, spiniform tooth-papille ; and
on each side of the mouth-angle is a close line of small mouth-papille, whereof
the inner ones are bead-like, while the two outermost are wider and somewhat
flattened. The small, rounded mouth-shields and the.side mouth-shields are
completely covered by a close granulation. First under arm-plate about half
as large as those beyond, of a heart-shape, with the point inward ; the rest are
rather small, somewhat broader than long, much wider without than within,
having the outer side curved, lateral sides re-enteringly curved and a truncated
angle within. Side arm-plates small, clinging close to arm, widely separated
above, nearly meeting below. Upper arm-plates four-sided, twice as broad as
long, much wider without than within, with outer side gently curved and lat-
erals straight. Disk pentagonal, flat, densely and uniformly covered with an
extremely fine granulation, 20 or 25 grains in the length of 1 mm.; this gran-
ulation extends over the entire mouth angle quite to the bases of the mouth-
papilla. Six very short arm-spines, growing longer from above downward ;
the upper ones are rounded and peg-like ; the lowest ones somewhat flattened,
and scarcely more than half as long as a joint. One oval tentacle-scale. Color
in alcohol, light greenish gray.
Station 142, 150 fathoms, 6 specimens.
OPHIOTHRIX Mitt. & Troscu.
Ophiothrix aristulata sp. nov.
Plate XV. Figs. 421-424.
Special Marks. — Ten moderately stout, feebly thorny, scarcely tapering arm-
spines. Disk, except the large radial shields, densely set with short, slightly
rough spines.
Description of an Individual (Station 142).—— Diameter of disk 14 mm.
Width of arm near disk 3mm. There are about thirty tooth-papille which
are pointed, and are arranged, as ysual, in a vertical oval, the exterior line on
either side composed of ten or eleven longer ones, while a similar number of
shorter ones, arranged in twos at the centre, and in a single line above and be-
low, fill closely the middle space. Three short, thick, squarish teeth. Mouth-
MUSEUM OF COMPARATIVE ZOOLOGY. 51
shield well marked, of a transverse diamond-shape, with rounded corners. Side
mouth-shields thick and slightly swollen, rather wide, nearly or quite meeting
within, tapering gently inward. Under arm-plates somewhat wider than long,
with a wide curve without, short re-enteringly curved laterals, and straight
inner laterals sloping towards the median line. Side arm-plates presenting a
moderately prominent spine-crest. Upper arm-plates wider than long, slightly
overlapping, of a transverse diamond-shape, with corners rounded or truncated ;
each plate has a median ridge, which gives to the upper arm a carinate look.
Disk thick and strongly lobed in the interbrachial spaces ; its upper surface
occupied chiefly by large radial shields, which are long triangular, with a length
to breadth of 5:3 ; they unite without, where each has a lobe projecting over
the arm, separated within by a narrow wedge of scales bearing one or two rows
of short, slightly rough spines: similar but somewhat longer spines densely
clothe the centre and interbrachial spaces, passing over the margin and investing
the outer portion of the naked surface below ; the longest spines are 1.7 mm.
Ten moderately stout, scarcely sapering, somewhat flattened, translucent arm-
spines, bearing feeble thorns on their edges; the uppermost and lowest are
minute, the rest diminish in length from the third downward ; lengths to that
of an under arm-plate, .8, 3.6, 4.6, 3.6, 3, 3, 2.6,2,1,.8:1. The first tentacle-
pore has no scales ; those beyond have a minute lip-like one in the angle of the
under and side arm-plates. Color in alcohol, above, pale purplish pink, the
side arm-plates and outer edges of radial shields marked with darker ; below,
much paler.
Station 142, 150 fathoms, 12+ specimens. Station 161 (var. with coarser
spines), 38 fathoms, 2 specimens. Station 163 (var.), 120 fathoms, 5 speci-
mens.
The species is readily distinguished from O. capensis by lacking the black
stripe on the arm, and by having arm-spines serrated their whole length.
Ophiothrix capillaris sp. nov.
Plate XIV. Figs. 401-404.
Special Marks.— Very large, with nine very delicate, translucent arm-spines,
whereof the upper ones are extremely long. Disk set with minute stumps,
which are few and scattered on the large radial shields.
Description of an Individual (Station 204).— Diameter of disk 22 mm.
Width of arm near disk, 4.8 mm. The vertical oval has over fifty tooth-papille
of various sizes, those in the lower half being minute, crowded, and grain-like,
while those on the margin of the upper half are large and thiek, and project
beyond the median papilla. Four flat teeth, with rounded cutting edge ; the
uppermost and lowest narrowest. Mouth-shields small, much broader than
long, bounded’ by a gentle curve without and an obtuse angle within ; length
to breadth .8 : 1.8. Under arm-plates small, narrow, about as long as broad,
eight-sided, with angles mofe or less rounded and lateral sides a little re-enter-
ingly curved. Side arm-plates with a well-marked spine-ridge. Upper arm-
52 BULLETIN OF THE
plates about as broad as long, of a short diamond-shape, with angles rounded,
rising on the median line ina low ridge and microscopically tuberculous. Disk
round and flat, scarcely lobed in interbrachial spaces, more or less closely heset
above and below with minute stumps bearing an irregular crown of thorns;
on the radial ‘shields they are much more scattered, smaller, and less thorny,
and next the genital openings there are none, The radial shields, whose out-
lines are distinguishable through their covering, are triangular and very large, _
with a small lobe where they unite over the arm ; inwardly they diverge, and
sometimes again bend together so as nearly or quite to reunite; length to breadth
9: 4.5. On joints next disk there are nine slender, glassy, translucent, slightly
flattened feebly thorny spines, whereof the uppermost are extremely long and
elegant; those below progressively shorter ; lengths to that of an under arm--
plate, 15.5, 15, 13, 9, 7, 6, 5, 3,1.7: 1.7. One small, blade-like tentacle-scale
in the angle of the under and side arm-plates. Color in alcohol, above, pale
brownish pink ; below, very pale yellowish brown ; along upper side of arm
is a wide, brown stripe, whose edges are darkest.
Station 204, 100-115 fathoms, 3 specimens. Cebu ; 100 fathoms.
O. capillaris belongs near O. comata and O, Suensonii. It has an arm-stripe
like that of the former, but has little stumps on the disk instead of hair-like
spines.
Ophiothrix berberis sp. nov.
Plate XV. Figs. 425-428.
Special Marks. —Seven short, blunt, much flattened, strongly toothed arm-
spines. Radial shields and interbrachial spaces below nearly or quite naked.
Rest of disk set with short stumps bearing a crown of thorns.
Description of an Individual (Station 192). — Diameter of disk 9mm. Width
of arm near disk 2.6mm. Length of arm about 58mm. The vertical oval
has about seventeen stout, blunt, nearly equal tooth-papilla, whereof the mar-
ginal ones are scarcely longer than those in the middle. Three squarish, rather
thin teeth. Mouth-shields broader than long, with an obtuse angle inward and
a gentle curve without ; length to breadth, 1 : 1.5. Side mouth-shields rather
narrow, slightly swollen, wider without than within, where they scarcely meet.
First under arm-plate unusually large, nearly equalling the second, squarish,
with rounded corners and an obtuse angle within. The plates increase in size
to the seventh, which is broader than long, bounded without by a wide curve,
and within by a truncated angle ; length to breadth .7 : 1.1. Side arm-plates
furnished with a low thick spine ridge. Upper arm-plates transverse diamond-
shaped, overlapping, having outer angle rounded and inner one truncated ;
length to breadth .7 : 1.4. Disk rather flat, lobed in the interbrachial spaces,
which, below, are nearly naked, as are the radial shields, while the remainder
of the upper disk is densely covered with short, minute stumps, each bearing a
crown of three or four thorns, or, rarely, a fork of two longer thorns. Radial
shields long triangular, just touching without, diverging gently inward ; length
to breadth 2.7 : 1:7. Seven, short, blunt, much flattened arm-spines, bearing
MUSEUM OF COMPARATIVE ZOOLOGY. 53
strong thorns on their edges; the second one is longest, and those below grow
gradually shorter ; lengths to that of an under arm-plate, 2.3, 3.5, 2.5, 2.2, 1.7,
1.5,.7.:.7. One minute tentacle-scale. Color in alcohol, above, disk pale
greenish gray, arms of a faint pink.
Station 192, 129 fathoms, 1 specimen. Station, Cebu, Philippines, 95 - 100
fathoms, 1 specimen.
Ophiothrix csespitosa sp. nov.
Special Marks. — Nine short, stout, much flattened, strongly toothed arm-
spines. The puffed disk and small radial shields are set with short spines.
Upper arm-plates transverse diamond-shaped, with lateral angles sharp.
- Description of an Individual (Port Jackson).— Diameter of disk 7 mm.
Length of arm 28 mm. Width of arm near disk 1.5. The vertical oval has
about sixteen stout, blunt, nearly equal tooth-papille, whereof four or five are
on the median line, and nearly as large as those on the margin. Four rather
thin, squarish teeth, with a cutting edge making an obtuse angle. Mouth-
shields small, closely joined to surrounding parts, broader than long, of a trans-
verse, rounded oval shape, having a curve without and a very blunt, obtuse angle
within. Side mouth-shields narrow, wider without than within, where they
meet. Under arm-plates with ill-marked outlines of a rude, transverse oval
form, with a curve without, lateral sides a little indented and the inner side
vaguely angular. Side arm-plates with a low spine ridge. Upper arm-plates
much wider than long, transverse diamond-shape, with lateral angles sharp and
the outer one rounded ; length to breadth .5 : 1.1. Disk thick, and pufted in
the interbrachial spaces, thickly set near the margin with short, stout, stump~
like spines rough at ends and sides, the longest .5 mm. in length. Towards the
centre the spines grow fewer, and the middle region has scarcely any, so that
the rounded overlapping scaling is conspicuous ; next the mouth-shields, also,
there are no spines. Radial shields small and triangular, much obscured by
the short spines. Nine short, translucent, rather stout, blunt, flattened arm-
spines, bearing pretty strong thorns on their edges ; lengths to that of an under
arm-plate, .8, 1.5, 1.8, 1.7, 1.3, 1.1, .9, .7,.4 : .5. One minute tentacle-scale at
angle of under and side arm-plates. Color in alcohol, above, disk faint green-
ish ; arms banded with lighter and darker yellowish brown.
‘Station, Port Jackson, 2-10 fathoms, 3 specimens.
In its disk this species resembles O. triglochis, but the arm-spines are much
flatter and more toothed, and the upper arm-plates of a different shape.
Ophiothrix violacea Miu. & Troscn.
Ophiothriz violacea. Syst. Asterid., p. 115.
Off Brazil, 7-20 fathoms, 12+ specimens. Station 36, off Bermuda, 32
fathoms, 3 specimens. Fernando Noronha (same species ?), shallow water,
1 specimen,
54 BULLETIN OF THE
Ophiothrix Liitkeni? Wyv. Tom.
Ophiothrix Liitkeni. Depths of the Sea, 1872, p. 100.
Station 75, 450 fathoms, 1 specimen (young).
Ophiothrix propinqua Lym.
Ophiothrix propinqua. Proc. Bost. Soc. Nat. Hist., VIIL., 1861, p. 83.
Tongatabu, 18 fathoms, 3 specimens (red var.). Fiji, Levuka Reefs, 2 speci-
mens. |
Ophiothrix purpurea v. Marrens.
Ophiothrix purpurea. Monatsber. Kon. Akad., 1867, p. 346.
Station 176, 1450 fathoms [error? Sta. 177, 63 fms. ?], 3 specimens. Banda,
1 specimen.
Ophiothrix nereidina Mutu. & Trosc#.
Ophiothriz nereidina. Systerid. Ast., p. 115.
Zamboanga, Philippine Isl., 10 fathoms, 4 specimens.
Ophiothrix stelligera Lym.
Ophiothriz stelligera. Bull. Mus. Comp. Zoél., III. 10, p. 237.
Aug. 7, 1874, 6 specimens. Station 186, 8 fathoms, 1 specimen. Arafura
Sea, 1 specimen (same species?). Zamboanga, 10 fathoms, 1 specimen.
Ophiothrix Suensonii Lrx.
Ophiothriz Suensonii. Vid. Meddel., 1856, p. 16.
Station 36, 32 fathoms, 2 specimens.
Ophiothrix pusilla Lym.
Ophiothriz pusilla. Bull. Mus. Comp. Zodl., III. 10, p. 235.
Station 208, 18 fathoms, 3 specimens.
Ophiothrix longipeda Mutt. & Troscu.
Ophiothrix longipeda. Syst. Asterid., p. 113.
Station 186, 8 fathoms, 2 specimens. Ternate Shore, 1 specimen. 7 Aug.,
1874, 1 specimen. Station 188, 28 fathoms, 2 specimens. Tongatabu, 18 fathoms,
1 specimen (same species?). Amboyna, 100 fathoms, 10 specimens (same
species?). Zamboanga, 10 fathoms, 1 specimen.
Ophiothrix galatez? Lrx.
Ophiothriz galatea. Ophiurid. Nov. Descr., 1872, p. 108.
Tongatabu, 18 fathoms.
‘MUSEUM OF COMPARATIVE ZOOLOGY. 5d
Ophiothrix striolata GRUBE.
Ophiothrix striolata. Verhandl. Schlesisch. Ges., 1867, Pt. III. p. 99.
Station 208, 18 fathoms, 1 specimen. Fatcabsasase Philippines, 10 fathoms,
1 specimen.
Ophiothrix Martensi Lym.
Ophiothrix Martensi. Bull. Mus. Comp. Zool, ILI. 10, p. 234.
“ Aug. 7, 1874, 4 specimens.
Ophiothrix exigua Lym.
Ophiothrix exigua. Bull. Mus. Comp. Zool., [11]. 10, p. 236.
Station 188, 28 fathoms, 1 specimen. Station 208, 18 fathoms, 1 specimen.
Ophiothrix ciliaris? Mui. & Troscu
Ophiothrix ciliaris. Syst. Asterid., p. 114, Lym. Bull. Mus. Comp. Zodl,
III. 10, p. 233, Pl. IV. figs. 29 - 32.
Cebu, 95 - 100 fathoms, 1 specimen.
Ophiothrix triglochis Miu... & Trosca.
Ophiothrix triglochis. Syst. Asterid., p. 114.
Simon Bay, 5-18 fathoms, 3 specimens.
OPHIOCHITON Lym.
Ophiochiton lentus sp. nov.
Plate XIV. Figs. 398-400.
Special Marks. —'Three stout arm-spines. Under arm-plates thickened, but
not forming a distinct ridge. Scaling of disk smooth and uniform.
Description of an Individual (Station 171). —Diameter of disk 13 mm.
Width of arm close to disk 2.6mm. There are eleven short, sharp, stout,
close-set mouth-papille on each angle, the two outermost and the one at the apex
being a little larger than the rest. Mouth-shields about as broad as long, of a
rounded heart-shape. Side mouth-shields extremely narrow, bent, wider without
than within, where they meet. Under arm-plates large, swollen but not ridged,
wider without than within, with lateral sides re-enteringly curved. Side arm-
plates short and stout, with a low thick spine-ridge. Upper arm-plates twice as
broad as long, of a fan-shape, with inner angle truncated, or a diamond-shape with
much rounded angles. Disk round, smooth, and flat, covered with small, pretty
uniform, rounded, overlapping scales, 2 or 3 in the length of 1mm. Radial shields
small, twice as long as broad, with much rounded corners, separated their entire
length hy two large round scales ; length to breadth2:1. Interbrachial spaces
below covered with scaling similar to but finer than that above. Genital open-
ings. long, extending from outer corners of mouth-shield, where there are a few
56 BULLETIN OF THE
minute papille, to margin of disk. Three stout, blunt, cylindrical, tapering,
nearly equal arm-spines, about as long as an arm-joint. Two round, flat, ten-
tacle-scales on the side arm-plate, whereof the one next the under arm-plate
is much the smaller. Color in alcohol, pale gray.
Station 171, 600 fathoms, 1 specimen.
OPHIOGLYPHA Lym.
Ophioglypha meridionalis sp. nov.
Plate XVI. Figs. 447 - 449.
Special Marks.-—Disk rather flat, covered with large imbricated scales.
Arm-comb of minute bead-like papille, scarcely to be seen above, but con-
tinuous along edge of genital scale. Three peg-like arm-spines less than half
as long as a joint. Only one tentacle-scale beyond the mouth-tentacles.
Description of an Individual (Station 320). — Diameter of disk 4mm. Length
of arm about 12mm. Width of arm close to the disk .7 mm. Five small,
short, broad, flat, close-set mouth-papille on each side of the mouth-angle, and
one pointed and similar to the teeth at the apex. Mouth-shields somewhat
swollen, about as broad as long, with a curve without and an obtuse angle in-
ward. Side mouth-shields short, straight, meeting by their full width within,
occupying only the inner angle of mouth-shield. First under arm-plate blunt
heart-shaped, quite as large as, or larger than, the second, which is pentagonal,
with inner angle truncated, outer side gently curved, and laterals re-enteringly
curved ; one third out on the arm the under plates are small, much wider than
long, bounded by a broad curve withont and with a little peak inward. Side
arm-plates large and thick, meeting broadly below beyond the second arm-
plate, and touching above beyond the third plate. Upper arm-plates long
wedge-shaped, with a clean curve outward and a sharp angle within. Disk
rounded, rather flat and only a little arched above, covered by large slightly
swollen scales, whereof the primary plates form a conspicuous rosette, radiating
from which there usually is, in each interbrachial space, a row of three over-
lapping scales. Radial-shields as broad as long, ‘sunken, rounded, with a faint
angle inward ; joined without, separated by a wedge-scale within; they are
smaller than the large disk-scales. Below, the scales are similar, eight or nine
in each interbrachial space. Papille along edge of genital scale minute,
bead-like, and continuous; only one or two, and sometimes none, can be
seen from the upper surface. Three small, nearly equal, peg-like arm-spines,
less than half the length of a side arm-plate. Five small, close-set tentacle-
scales to pores of mouth-tentacles, three on one side and two on the other ; the
pores beyond have but onesmall, rounded scale. Color in alcohol, straw.
Station 320, 600 fathoms, 1 specimen.
The single specimen, though well characterized, was perhaps not fully
grown. It is the southern cousin of O. robusta, from which it differs in shorter
arm-spines, more swollen disk-scales, smaller mouth-papillz, and fewer tentacle-
scales,
MUSEUM OF COMPARATIVE ZOOLOGY. 1 oF
OPHIACANTHA .MUttt. & Troscu.
Ophiacantha discoidea sp. nov.
Plate XV. Figs. 405 - 407.
Special Marks. — Seven or eight slender, translucent, nearly smooth arm-
spines. A small spine-like tentacle-scale. Disk densely set with minute
stumps crowned with thorns.
Description of an Individual (Station 190). — Diameter of disk, 4.7 mm.
Arms broken ; they were plainly long, because, in their first 15 mm. there was
scarcely any tapering. Width of arm near disk 1mm. Three cylindrical,
blunt, peg-like mouth-papillz on each side, and a similar but longer one at
apex of mouth-angle. Teeth longer than wide, with a rounded cutting edge.
Mouth-shields broader than long, regular heart-shaped, with point inwards ;
length to breadth, .7:1. Side mouth-shields very wide without, and overlap-
ping the first under arm-plate, but tapering to a thin point within, where they
scarcely meet. First under arm-plate longer than broad, and somewhat over-
lapped by side mouth-shields ; the plates just beyond are much wider than
long, of a wide axe-shape, with a broad curve without, short re-entering curves
on the sides, and an obtuse angle within. Side arm-plates meeting above and
below, stout and flaring, with a strong spine-crest. Upper arm-plates fan-
shaped, with the angle inward ; widely separated. Disk nearly round, a little
puffed, closely and evenly set, except in the middle, with very short micro-
scopic stumps crowned with 3 or 4 littlethorns. No scales or radial shields ap-
pear in the alcoholic specimen. Seven or eight slender, pointed, translucent,
nearly smooth arm-spines, whereof the two uppermost are nearly as long as
two joints ; while those below gradually diminish in length to the lowest,
which is two thirds as long as a joint. One narrow, pointed tentacle-scale.
Color in alcohol, pale brownish gray.
Station 190, 49 fathoms, 1 specimen.
This species stands nearest, perhaps, to O. cosmica, from which it is distin-
guished by different under arm-plates, smaller side mouth-shields, stouter disk-
stumps, and a very narrow spine-like tentacle-scale.
Ophiacantha Valenciennesi sp. nov.
Plate XV. Figs. 408-410. |
Special Marks. — Disk ‘evenly granulated above. Seven long, slender, much
flattened arm-spines. Outer mouth-papilla spatula-like and covering the pore
of the mouth-tentacle.
Description of an Individual (Station 192).— Diameter of disk 11 mm.
Length of arm 50mm. Width of arm near disk 3mm. Twelve mouth-papille
to each angle ; of these the outermost one on either side is wide, like a short
spatula, and is plainly the scale of the mouth-tentacle ; the next four papille
58 BULLETIN OF THE
are sharp and peg-like, the pair at apex of angle are thickened and conical.
Five flat teeth, a little longer than wide, with a curved cutting edge. Mouth-
shields long heart-shaped, or broad spear-head shaped ; length to breadth 1.5:
1.2. Side mouth-shields large and three-sided, wide without, tapering inward,
where they nearly or quite meet. First under arm-plate small and wider than
long ; plates beyond, wide pentagonal, with outer side gently curved, laterals
re-enteringly curved, 4nd inner angle so obtuse and rounded as to be almost a
gentle curve. Side arm-plates barely meeting below, separated above, rising in
a thick abrupt spine-ridge. Upper arm-plates small, thick, and fan-shaped,
with the angle inward. Disk thick and puffed, covered above by an even
granulation, 9 or 10 grains in the length of 1 mm. On removing these, there
is disclosed a smooth coat of very thin scales, about 5 in the length of 1 mm.,
which cover the radial shields, except their outer ends ; interbrachial spaces
below without grains, and covered with scales still finer than those above.
Seven slender, much flattened arm-spines, slightly rough on the edges; the
uppermost one extremely long, sometimes equal to five arm-joints, diminishing
to the lowest, which is longer than one joint. Two large, oblong, slightly pointed
tentacle-scales. Color in aleohol, pale brown above, much lighter below.
Station 192, 129 fathoms, 1 specimen.
Ophiacantha Normani sp. nov.
Plate XV. Figs. 414-416.
Special Marks. — Disk distinctly scaled and sparsely granulated, and with
small, separated radial shields. A single row of grains along the outer edge
of the basal upper arm-plates. Four smooth, slender spines, the upper ones
longest.
Description of an Individual (Station 232).— Diameter of disk 12.5 mm.
Length of arm about 40mm. Width of arm next disk 2.6mm. Seven widely
spaced, cylindrical, tapering, peg-like mouth-papille, three on each side, and
one at apex of mouth-angle. Mouth-shields a little broader than long, thick and
_ Square, with a little peak without and within ; length to breadth 1: 2. Side
mouth-shields long and narrow, their outer end wedged between the first and
second under arm-plates ; not quite meeting within. First under arm-plate well
marked, of a rounded triangular shape, with the point outward; third plate, .
and those just beyond it, broader than long, bounded without by a curve, on the
sides by re-entering curves, and within by an angle; length to breadth (4th
plate) 1.3: 1.7. Side arm-plates with a swollen spine-ridge, meeting below,
but separated above, stout, and, like the under plates, microscopically tuber-
culouss Upper arm-plates about as broad as long, short wedge-shaped, with
outer side curved and a blunt angle within ; the first three or four have,
along their outer margin, a single row of rounded grains, Disk flat, somewhat
angular, covered with well marked, pretty equal, overlapping scales, whose sur-
face is sparsely set with rounded grains, similar to those of the upper arm-plates ;
interbrachial spaces below similarly covered, except that the scales are smaller
MUSEUM OF COMPARATIVE ZOOLOGY. 59
and obscured by skin. Radial shields small, ovoid, as long as broad, widely
separated by a wedge of scales ; length to breadth 1.7: 1.3. Genital openings
wide, and extending quite from the mouth-shield to the disk margin. Four
smooth, cylindrical, rather slender, blunt, tapering arm-spines, whereof the
lowest is as long as an arm-joint, the two upper ones as long as a joint anda
half, and the third intermediate. One rather large oval tentacle-scale. Color
in alcohol, gray, with arm inclining to straw.
‘ Station 232, 345 fathoms, 12+ specimens. Station 235, 565 fathoms, .
1 specimen.
Ophiacantha abnormis sp. nov.
Plate XV. Figs. 411-413.
Special Marks. — Mouth-angles elongated, bearing, toward the apex, 12 or 14
slender, pointed papilla. Six long, smooth, slender arm-spines. Disk sparsely
set with very short spines.
Description of an Individual (Station 207).— Diameter of disk 11 mm.
Length of arm, which is very attenuated near its end, 73 mm. Width of arm
close to disk, without spines, 25 mm. Mouth-angles elongated, having no
papille on their outer part near the mouth-tentacles, but on their inner portion
bearing 4 or 5 slender, spaced papille on each side, and a cluster of 3 or 4 at
the apex. Teeth wide and large, with a broad cutting edge. Mouth-shields
broad triangular, with a small peak on the outer edge, and blunt angle within.
Side mouth-shields short and extremely narrow, just meeting within. Under
arm-plates thin and sunken, pentagonal, with a broad angle inward, outer
edge straight, and deep re-entering curves on the lateral sides. Beyond
the third, they are separated by the side arm-plates, which meet below and
above and have a high, wide spine-ridge. Upper arm-plates triangular, some-
what swollen, with an angle inward, sharp lateral corners, and broad nearly
straight outer edge, which on the basal plates bears two minute spines. Disk
flat, having re-entering curves in the interbrachial spaces, and rather sparsely
set with minute, short, blunt spines, which are fewer below. The outer ends
of radial shields are exposed over the base of each arm. Genital openings long
and large, extending from mouth-shield to disk margin. Six long, slender,
smooth, cylindrical, tapering arm-spines, of which the two upper ones are as
long as two arm-joints, thence diminishing in length to the lowest, which is
about as long as half a joint. Pores large and tentacles very long ; on basal
ones are two scales, of a pointed oval shape ; on those beyond, only one. Color
in alcohol, straw.
Station 207, 700 fathoms, 12+ specimens. Station 210, 375 fathoms,
5 specimens.
In its elongated mouth-angles, this species somewhat resembles O. hirsuta,
but its arm-spines are smooth and in all ways different.
60 BULLETIN OF THE
NOTE ON THE STRUCTURE OF ASTROPHYTIDA.
In very early youth the Astrophytons bear a close resemblance to true
Ophiurans, but they rapidly change with growth. Their structure will be
more fully treated in the main work, and only two or three points of differ-
ence will here be suggested.
First, as to the arm covering. The young tip of an Astrophyton twig has
the side arm-plates quite encircling it (Fig. 495), just as in an Ophiuran ; but
already at the base of the same twig this plate is quite subordinate (Fig. 494 7),
while at the base of the arm (Fig. 493 7) it occupies only the under surface,
while the arm has risen in a high arch above it. It is not otherwise in the
simple-armed Astroschema (Fig. 4917). The upper arm-plates have no regular
form, or stated mode of division ; but doubtless they are represented by a casing
of very irregular scale-like pieces, to be found on the terminal branches of
Astrophyton, and in the narrow belts of broken plates found in A stroschema
(Fig. 491). The under arm-plates are extremely variable ; in the type of
Euryale asperum they are essentially in one piece, and are constant to the end
of the branches (Fig. 499 4), while for the type of Astrophyton costosum they
are quite wanting, except perhaps the first one (Fig. 4974), and are replaced
by the large side arm-plates (Fig. 497 7) ; in the cold-water Astrophytons, such
as A. Agassizii, they are plainly distinguished in the young, though divided in
three pieces (Fig. 492 2, h). To such a structure of arm-plates the nearest
approach among Ophiurans would perhaps be Ophiomyza.
Secondly, as to the arm-spines. There are found, at the extreme tip of a
twig of Astrophyton (Fig. 495), little hooklets on the side arm-plates ; when
the arm has risen above the plate, and become quite distinct from it, there
are found two or more large hooks (Fig. 494 q), which are the homo-
logues of tentacle-scales, and which, nearer the base of the arm, usually become
blunt spines (Fig. 493 q). In addition to these there are found on the twigs,
in the true Astrophytons, Astroclon, Astrocnida, and among the simple-armed,
in Astrogomphus, Astroporpa, Astrochele, and Astrotoma, two zones or belts of
raised grains, each grain bearing a hooklet (Fig. 494). These belts of hook-
bearing grains are therefore characteristic of a group among Astrophytide ;
while another is destitute of them, as Euryale asperum (Figs. 500, 501), Tri-
chaster, Astroceras, Astroschema (Fig. 491), Ophiocreas, and Astronyz.
Thirdly, the mouth-shields among Astrophytons are quite subordinate, al-
though so important among Ophiurans. Frequently there is but one (Fig.
492 a), and the position is very variable. The side mouth-shields, on the con-
trary, are usually very prominent (Figs. 492, 497, 499 b) ; so large are they in
Trichaster that Miller and Troschel mistook them for a mouth-shield cut in
two. The entirely different structure of Euryale asperum as exhibited in the
figure (499), and especially the elongated side arm-plates (Fig. 501 7), absence
of hook-bearing grains, and distinct build of mouth and under arm-plates:
makes it advisable to remove the species from Astrophyton and restore to it the
name Euryale. It is a question, also, whether the tropical Astrophytons
MUSEUM OF COMPARATIVE ZOOLOGY. 61
should not be generically distinguished. I have already shown, in considering
those of the Hassler Expedition, the very different character of the arms
(Figs. 496, 498), and the arrangement of their underlying hard parts is cer-
tainly quite different in the two (Figs. 492, 497).
ASTROTOMA Lym.
Astrotoma Murrayi sp. nov.
Plate XVIII. Figs. 474 - 476.
Special Marks. — Large tubercles, or smooth warts, on upper side of disk.
No hooklets on belts of grains on arms, except close to their tip. Clusters of
grains in interbrachial spaces next mouth.
Description of an Individual (Station 194).— Diameter of disk 29 mm.
Length of arm 280 mm. Width of arm near disk 7 mm. Height of arm near
disk 7mm Apex of mouth-angle, embracing all the region of the jaw-plate,
densely set with short, sharp, nearly equal, spine-like papille, thirty or more
in number, and arranged in transverse rows of three or four. Lower surface
and a part of the sides of the protuberant mouth-angles closely set with rounded
and sometimes elongated grains. One round madreporic mouth-shield, 1.5 mm,
in diameter, lying on the margin of the horizontal mouth-region, where it is
separated from the vertical interbrachial space by a fold of skin stretched be-
tween the bases of the arms. Arms high, and tapering gradually to their tips,
covered above and on the sides by belts of granules alternately raised and
sunken. In the former the granules are larger and more distinct, and are more
or less regularly arranged in four rows, whereof two at tip of arm bear minute,
simple hooks, which, however, are soon rubbed off. In the latter, the granules
are minute and arranged as a smooth pavement, in which appear many oblong
holes or depressions. On its under surface the arm is covered by a cross-
wrinkled, calcified skin, on which are scattered granules. Disk flat and angu-
lar, with re-entering curves in the interbrachial spaces; the radial shields,
whose outlines are vaguely defined, are broad, and run nearly or quite to the
centre. The upper surface is covered by a smooth pavement of small, soldered
grains, among which appear small oblong depressions, and on whose surface
are scattered a few. large, smooth tubercles. The interbrachial spaces below
are covered by a clump of large, coarse grains ; at the inner end of each of these
spaces is a deep, transverse hollow, at either extremity of which is a short,
genital opening. Between the mouth-slit and lower margin of disk there are
no tentacle-scales ; but, beyond, each pore has four, rarely five, stout, smooth,
peg-like scales, lying side by side, arid nearly as long as an arm-joint ; nearer
tip of arm there are but three. Color in alcohol, reddish brown, the disk
tubercles and clumps of grains about mouth being darker.
Station 194, 200 fathoms, 1 specimen.
“
62 BULLETIN OF THE
ASTROCERAS * gen. nov.
Disk and arms covered with smooth, soft skin. Disk small ; its interbra-
chial outlines re-enteringly curved; radial shields narrow and rather high,
running nearly to centre. Arms somewhat knotted by a contraction between
each pair of joints. Upper arm-plates divided in halves like high ribs, bearing
a jointed spine at their upper end. Side arm-plates, towards middle of arm,
having a long process to which are articulated the two spine-like tentacle-
scales. Teeth. A clump of grains on sides of mouth- angles, answering to
mouth-papille. Two vertical genital openings.
Astroceras stands next Ophiocreas and Astroschema. By its peculiar elon-
gated side arm-plates bearing spine-like, rough tentacle-scales, and the large
spines on the upper surface of the arm, it resembles the branching Ewryale
asperum.
Astroceras pergamena sp. nov.
Plate XVIII. Figs. 478 -480. e
Special Marks. — The smooth skin is translucent, allowing the underlying
parts to be seen. The upper ends of the halves of the upper arm-plates pro-
ject, and bear a stout spine. Tentacle-scales thick, rough ended, and nearly
equal in size. On the sides of the mouth-angle are elongated grains answering
to mouth-papille.
Description of an Individual (Station 235).— Diameter of disk 19 mm.
Length of arm about 100 mm. Width of arm at base 2 nm. ; height of same
2.5mm. High up on the sides of the mouth-angles are elongated grains, irreg-
ularly arranged and answering to mouth-papille, while at the apex is the low-
est tooth, flat and shaped like a wide spear-head. Mouth-shields very small,
triangular, with a rounded angle inward and outer edge straight. Side mouth-
shields very large and swollen, narrower without, meeting broadly within ; both
they and the mouth-shields are obscured by skin. Under arm-plates small,
and squarish, and occupying only a part of the length of a joint. Side arm-
plates nearly or quite meeting below, swollen and rounded, with a small pro-
jection to carry the two spine-like tentacle-scales ; further out, on the arm,
this projection is much elongated, forming an articulating process. Upper arm-
plates represented by two rib-like ridges, which do not meet above, but project
over the upper level of the arm, and bear a large, club-like, rough spine about
1.2 mm. long. Disk thin, and with deep constrictions in the interbrachial
spaces. The smooth translucent skin allows the long and narrow radial shields
to be seen ; they are pointed within where they do not meet, and are separated
their entire length; at their outer end they are elevated and carry a jointed
spine, similar to that of the arms. The first pair of arm-pores has no tentacle-
scales ; but those beyond have two, which are thick and club-shaped, with
* dorhp, star; xépas, horn.
MUSEUM OF COMPARATIVE ZOOLOGY. 63
rough ends, and, unlike those of Astroschema, are nearly equal in size, and
not much elongated towards the middle of the arm, where they bear bunches
of minute hooks on their ends, and have a pedunculated look, owing to the
elongation of the side arm-plates. Color in alcohol, light yellowish brown.
Station 235, 565 fathoms, 1 specimen.
OPHIOCREAS Lym.
In Ophiocreas and Astroschema the mouth gives almost no specific indica-
tions. It is by the character of the skin, or by the nature of its granulation,
the thickness and Jength of the arms, their comparative height and breadth,
and the form of the tentacle-scales and of the radial shields, that we get good
specific marks. |
Ophiocreas carnosus.
Plate XVI. Figs. 435 - 438.
Special Marks. — Animal covered by a smooth, soft, wrinkled skin. Tenta-
cle-scales like rough-ended but not clubbed spines, which are short even at
middle of the arm.
Description of an Individual * (Station 308).— Diameter of disk 15 mm.
Length of arm 200 mm. Width of arm near disk 7 mm. ; height at the same
point6 mm. Mouth-angles so fleshy and puffed as to fill almost entirely the
slits ; at the apex appears a small peg-like tooth ; upper teeth wider and
spear-head shaped. On removing the thick, flabby skin, the usual large ob-
long side mouth-shields are seen, joined their entire length, except without,
where they diverge somewhat to give place to the little mouth-shield. The side
arm-plates are long, narrow, and curved, and meet fully below, separating the
small, irregular, transversely oblong under arm-plates ; at their upper end they
. support the tentacle-scales, and unite with the belt of thin scales which repre-
sents the upper arm-plate. Disk thick, rising a little above the level of the
arms, covered by a very thick, soft skin, which is especially wrinkled over the
side mouth-shields. The same skin covers the arms, and is there loose and
flabby. Radial shields narrow, rounded, thick and running quite to the cen-
tre. No tentacle-scale on first arm-pore ; the next five have one, in form of a
small, blunt, thick spine enveloped in a sort of skin bag ; beyond, there are
two, the lower of which, towards middle of arm, does not exceed 3 mm., and
has a rough, but scarcely clubbed end. Color in alcohol, brownish pink, ap-
proaching flesh-color.
Station 308, 175 fathoms, 12+- specimens.
* The specimen described is not of the same size as the one figured.
,
64 P BULLETIN OF THE
Ophiocreas caudatus sp. nov.
Plate XVI. Figs. 439 - 442.
Special Marks. — A large species. _ Arms to disk as 13 to 1. No tentacle-
scale on the first arm-joint; then for several joints only one, small and peg-
like ; thereafter two, which never grow very long. Skin thick.
Description of an Individual (Station 232).— Diameter of disk 22 mm.
Length of arm about 300mm. Width of arm close to disk 5.6mm. Height of
arm near base 5.5mm. Mouth-angles covered with very thick skin giving a
swollen look ; on their sides and above the second mouth-tentacle is a sort of
pavement of irregular flattened grains. , Twelve large thick teeth, longer than
wide, with cutting edge shaped like a rounded angle ; the two lowest are small-
est and are less flattened. Arm-joints obscurely indicated by the arm-bones,
whose outlines are seen through the skin. Arms broader above than below ;
covered with a thick skin, which, when partly dry, presents under the micro-
scope a minutely tuberculous surface. No tentacle-scale on first arm-joint ; be-
yond this there is only one, short and peg-like, for some distance, sometimes
as far as the thirteenth joint ; after which there are two, still short, and cased
in very thick bags of skin ; on last third of arm the scale of the brachial side
has become stout, thorny-ended, and much the longer (8 mm.). Disk thick
and angular, covered with thick skin similar to that of the arms, and having
interbrachial spaces re-enteringly curved. Radial shields high and narrow,
diverging from the centre of disk to sides of the arms. The genital openings
are long, extending from upper edge of disk to mouth-ring. Color in alcohol,
uniform pinkish brown.
Station 232, off Enosima, 340 fathoms, 2 specimens.
Another somewhat smaller specimen had already two tentacle-scales on the
fifth joint.
Ophiocreas abyssicola sp. nov.
Plate XVII. Figs. 470-473.
Special Marks. — Arms scarcely as high as wide, about eight times the
diameter of the disk. Skin quite smooth, with radial shields scarcely indicated
externally. Genital openings very short, and situated near the inner inter-
brachial angle.
Description of an Individual (Station 941). — Diameter of disk 7 mm.
Length of arm about 60mm. Width of arm close to disk 1.7 mm ; height of
same 1.2mm. Four or five short, flat grains above the second mouth-tentacle,
on the sides of each mouth-angle. Seven stout, nearly equal teeth, shaped
like a blunt spear-head. On removing the skin the small, irregular, rounded
mouth-shield, and large, longer than broad side mouth-shields, can be seen ;
the latter are often broken. Under arm-plates rather large, rounded, as broad
as long, closely soldered, and with vague outlines. Side arm-plates small,
MUSEUM OF COMPARATIVE ZOOLOGY. 65
rounded, and swollen, closely joined with the under arm-plates. Arm-joints
recognizable through the skin. Arms rounded and slender, tapering very
gradually to the end. Disk flat and somewhat angular, not rising above
level of arms, covered with soft, moderately thick skin. Radial shields shorter
and wider than in other species, separated their entire length, and very thin
and flat ; from the outside they are scarcely indicated, and they do not meet
in the centre. Two short, stout, bluntly pointed tentacle-scales, the lower one
longer, and both nearly naked. Two very short genital openings, about 5 mm.
long, near inner angle. When the skin is removed the genital plate and scale
are seen, the plate being rounded, much longer than broad, tapering from with-
out inward, and having the small, peg-like scale attached near its outer end.
Color in alcohol, pale straw.
Station 241, 2,300 fathoms, 5 specimens.
This species, well distinguished from others, is remarkable for the great
depth at which it lives. The genus is usually found not far below the 100-
fathom line, and 500 fathoms may be considered deep for it.
Ophiocreas cedipus sp. nov.
Plate XVI. Figs. 443 - 446.
Special Marks.— Arms about twenty times the diameter of disk, and slender,
except the base, which is swollen above, and contains the ovaries.
Description of an Individual (Station 344). — Diameter of disk 12 mm.
Length of arm about 250mm. Arm much swollen for the first four or five
joints next disk, where its width is 3.5 mm., then suddenly shrinking to 2mm.
with a height of 2mm. There are numerous small, flattened grains extending
along the sides’ of the mouth-angles, above the second mouth-tentacle. Eight
or nine broad, flat teeth, with well-rounded cutting edge, the two lowest being
much narrower and peg-like. On removing the skin the mouth-shield is seen
to be very small, a little longer than wide, with ends much rounded. Side
mouth-shields very large, much longer than wide, with ends much rounded.
Side mouth-shields very large, much longer than wide, somewhat swollen,
meeting within where they are narrowest. Under arm-plates composed of two
or more small pieces. Side arm-plates swollen, meeting below, and, at the
base of the arm, joined to thick, narrow, ridge-like upper arm-plates, which
arch upward, and nearly or quite meet on the median line. Disk angular and
flat, with re-entering marginal curves. Radial shields narrow and highly
arched, not quite meeting in the centre, covered with thin skin, which
under the microscope is seen to be set with fine points. Genital openings
large and wide, occupying the whole height of the disk. Where the skin is
removed the genital plate is seen to be long, very broad and thick, tapering
inward ; the genital scale is small and peg-like. At base of arm there is only
one tentacle-scale ; beyond, there are two, the upper one very small, and spini-
’ form, the lower one enclosed in a thick club-ended skin-bag.
On opening the singular swelling on the upper side of the base of the arm,
VOL. VI. —NO. 2. 5
66 BULLETIN OF THE
it is found to be a pouch full of large eggs, which are about .7mm. long. In
fact, the ovaries are in this species thus pushed beyond the disk, somewhat as in
Star-fishes.
‘ Color in alcohol, pinkish or yellowish brown.
Station 344, 420 fathoms, 3 specimens.
ASTROSCHEMA Lrx.
Astroschema horridum sp. nov.
Plate XVII. Figs. 458 - 461.
Special Marks. — Entire surface covered with little, swollen, oblong angular
plates or scales, bearing minute points. |
Description of a Specimen (Station 170). — Diameter of disk 12.5 mm.
Length of arm 195mm. Width of arm near disk 4.7mm; height of arm
4.2mm. Seven stout, thickened, rather small teeth, of the usual short spear-
head shape. The mouth-angles are paved with large, flattened, swollen grains,
but have no true papille. Arms nearly cylindrical, very slightly swollen for
their first 20 mm., beyond which they taper very regularly. They are evenly
and pretty closely beset with minute points, like little blunt spines, about 4
in the length of 1 mm.; these, on allowing the surface to dry, are seen to stand
on small, swollen, oblong, angular plates or scales, which may be considered as
exaggerated grains set with points. This covering continues quite to the end
of the arm, where, however, the grains are more rounded and without points.
Disk thick, rising a little above the arms, elegantly scalloped on its margin,
with large radial shields (ribs), which are thick, swollen, and projecting at
their outer ends, and taper inward to the centre, where they meet ; its surface
is paved with little oblong, angular, swollen plates or scales, rather coarser
than those of the arms, and bearing similar minute points. Genital openings
straight, and occupying about one half the height of the disk. Mouth-tentacles
enclosed in a tube of flat grains; the next pair has no tentacle-scale ; the next
one and those beyond have two, which are short at first, but about 40 mm. out
become somewhat suddenly elongated, the upper one, about 1.3 mm. in length,
remaining blunt spiniform, while the lower and larger takes on the form of a
cylinder 3 mm. long, with a rough, swollen end. The two lines of pores lie
closer together than usual, so that the furrow on the lower side of the arm is
narrow. Color in alcohol, pale reddish brown.
Station 170, 630 fathoms, 1 specimen.
Astroschema salix sp. nov.
Plate XVII. Figs. 466 - 469.
Special Marks.— Granulation fine, even, and close set; 7 or 8 grains in the
length of 1 mm. Disk flat, with ill-distinguished radial shields. At tip of
arm the lower tentacle-scale takes the form of a compound hook,
MUSEUM OF COMPARATIVE ZOOLOGY. 67
Description of an Individual (Station 170).— Diameter of disk 8.5 mm.
Length of arm 85 mm. Width of arm near disk 3 mm. Height of arm
2.4mm. Mouth-angles covered with minute, close, smooth granulation, and
bearing at their apex the usual wide spear-head shaped teeth. Arms wide
next disk, tapering rapidly for about 15 mm., and thence very gradually to
their tips; covered by a fine, even, smooth, close-set granulation, 7 or 8
grains in the length of 1mm. The skin, being thin, allows the outlines of the
joints to show through, especially near the ends. Disk flat, scarcely rising
above arms, and with a similar granulation, though rather looser on the
upper surface. Radial shields scarcely to be distinguished, except at their —
outer ends. The first pair of pores outside mouth-slit has no scale; the next
six have only one; those beyond two, whereof the inner and larger is cylin-
drizal, with a somewhat swollen, rough end, and attains, about two thirds out
on arm, a length of 1.8mm. At the tip, the lower scale takes on the form of a
flattened compound hook, with four curved teeth on its edge. Color in alcohol,
very pale brown.
Station 170, 520-630 fathoms, 1 specimen.
Astroschema brachiatum sp nov.
Plate XVII. Figs. 462-465.
Special Marks. — Arms twenty-four times the diameter of the disk, higher
than wide, with a smooth, even granulation, 6 to 9 grains in the length of
1 mm.
Description of an Individual (Station 33).— Diameter of disk 11 mm.
Length of arm 270 mm. Width of arm near disk 3mm. Height of arm at
same point 3.8 mm. The granulation of the disk is, as usual, projected over
the mouth-angles, but there are no conspicuous grains which simulate mouth-
papille. Teeth short, blunt, peg-like spines. Arms long, smooth, higher than
wide, cleanly arched, and with only faint joint-ridges; they are closely and
uniformly covered with a smooth granulation, 6 to 9 grains in the length of 1
mm. Disk high and arched, with well marked, somewhat elevated radial ribs,
running nearly to the centre. The granulation is about as on the arms. Geni-
tal openings rather short; their upper ends not reaching the level of the top of
the arm. No tentacle-scales (spines) on first pair of pores outside mouth-slit ;
the next two pairs have one scale, and those beyond two, of which the lower
one attains a maximum length of 2 mm., and hasa rough, slightly clubbed end.
Color in alcohol uniform chocolate-brown.
Station 33, 435 fathoms, 1 specimen.
_ This species stands between A. tenue and A. leve ; its arms are much thicker
than those of the former, and much longer than those of the latter.
68 BULLETIN OF THE
Astroschema tumidum sp. nov.
Plate XVII. Figs. 450 - 453.
Special Marks. — Disk and arms covered by regularly spaced, pointed, coni-
eal grains. The bases of the arms for two or three joints are strongly swollen.
Description of an Individual (Station 192).— Diameter of disk 8 mm.
Length of arm 135 mm. Greatest width of arm, close to disk, 3.7 mm.
Width, beyond the swelling, 2.3mm. Height of arm, at same point, 1.8 mm.
Seven or eight short, flat teeth, with a curved cutting edge ; the lowest one
smallest. The general granulation of the disk is continued in a somewhat
coarser form over the mouth-angles, and up their sides ; but there are no true
mouth-papille. Arms well rounded, without any flattened surface, strongly
swollen and ribbed, for the first two or three joints, but even and tapering be-
yond ; set with pointed conical grains which are regularly spaced, about 5 in
the length of 1 mm., and which rarely touch each other. Disk strongly con-
tracted in interbrachial spaces, and occupied chiefly by the high, wide radial
shields (or ribs) which run quite to the centre ; granulation somewhat more
sparse than on arms. On first arm-pore there is no tentacle ; the next has one,
cylindrical, tapering and blunt, with sometimes a second rudimentary one ; the
pores beyond have two, whereof the upper one is, as usual, much the smaller.
One third out on the arm, the larger scale attains a length of 2 mm., and is rough
at the end and slightly clubbed. Color in alcohol, pale yellowish brown, with
interbrachial spaces of disk gray.
Station 192, 129 fathoms, 1 specimen.
This species presents the same swelled base of the arm found in Ophiocreas
edipus, and doubtless for the same purpose, an egg-pouch. The genera As-
troschema and Ophiocreas though differing widely in their remote members, are,
in their proximate species, only distinguished by surface granulation in the
former.
Astroschems rubrum sp. nov.
Plate XVII. Figs. 454-457.
Special Marks. — Arms, at bases, not cleanly arched, but somewhat angular.
Mouth-angles puffed so as to nearly close the slits. Granulation fine, smooth,
and close-set, 6 or 7 in 1 mm. long. Tentacle scales short and scarcely club-
ended. |
Description of an Individual (Station 310).— Diameter of disk 12 mm.
Length of arm 160 mm. Width of arm near disk, 3.5mm. Height of arm
3.5mm. Mouth-angles so swollen as nearly to close the slits, and covered by
a smooth granulation much obscured by skin ; at the apex are small wide
teeth. Arms near base as high as wide and not cleanly rounded, but inclined to be
angular, and showing distinctly the outlines of arm-joints ; tapering uniformly ;
near their ends higher than wide; covered by a close-set, smooth, fine granula-
tion, which, at bases of arms and on disk, has 6 or 7 grains in the length
MUSEUM OF COMPARATIVE ZOOLOGY. 69
ofl mm. Disk thick, but flat on top, and rising but little above arms, covered
by a thin skin, which is finely, closely and evenly granulated. The radial
shields are faintly indicated by flat ridges running to the centre. Mouth-tenta-
cles enclosed in tubes ; the next have no scale; the next three or four have
but one ; those beyond, two, which at first are small and spiniform, and are
nowhere long, the lower one attaining a maximum length of 1.4 mm. with a
cylindrical form, and a rough scarcely swollen end. Color in alcohol, brown-
ish red, approaching flesh-color.
Station 310, 400 fathoms, 4 specimens on a Gorgonian near Brandella.
By its color and smooth surface O. rubrum may easily be mistaken for an
Ophiocreas.
ASTROCLON * gen. nov.
Arms beginning to branch at a considerable distance from the disk, and
having but few forks, nearly as in T'richaster. Disk rising well above the
arms, and granulated, as are the latter. The tips of the twigs are encircled at
each joint by a double belt of hook-bearing grains. Along the under surface
of the base of the arm are two longitudinal lines of large, transverse slits, a
pair to each joint, from which issue short tentacles; and above these on either
side is a row of peg-like tentacle-scales. Mouth-angles naked on their sides,
but with a bunch of spine-like papille at the apex. Two very large genital
openings in each interbrachial space.
Astroclon propugnatorist sp. nov.
Plate XVIII. Figs. 481 - 486.
Special Marks. — Animal covered above by a closely soldered granulation,
in which appear numerous dark patches, which are small, oblong, smooth
plates, sometimes raised like tubercles, and sometimes sunken. Toe. the
granulation is microscopic, and, on part of the under surface a arm, wanting.
Five short, wide, smooth tentacle-scales.
Description of an Individual (Station 192).— Diameter of disk 65 mm.
Length of arm: from disk to 1st fork, 160 mm. ; from Ist fork to 2d, 36 mm. ;
2d to 3d, 137 mm.; 3d to 4th, 26mm.; 4th to 5th, 16mm. ; 5th to 6th, 16 mm.;
6th to end, 16 mm.; total, 407 mm. Width of arm near disk 14 mm.; height
‘at same point 10mm. Mouth-angles small, and on their sides smooth, eae,
* dornp, star; krdv, twig.
t Dr. Carpenter has happily translated “Challenger” by mpéuaxos, the Homeric
word for a champion who stood in front of the line of battle and challenged the
leaders of the enemy. Propugnator is a verbal translation, although it seems usually
to signify rather a defender. I am told by high authority, however, that its
present use is allowable. Goliath was such a challenging champion, but he is de-
scribed in the Vulgate as vir spurius, an expression not applicable here.
70 BULLETIN OF THE
at the apex a vertical tuft of small, smooth, short, spine-like papille. From
near mouth to margin of disk the arms grow wider, but begin to taper from
that point. They are cleanly arched above, but flat on the lower surface, a:
large portion of which is occupied by the deep, oblong, transverse pits (the
largest 3.5 mm. long) on whose inner side stand the tentacles, so that this
surface presents the appearance of a central, narrow, radiating strip, on whose
sides are the tentacle-pits, arranged like the feathers of an arrow. This
central strip has a very fine granulation, nearly obscured by skin; but the
lateral region is quite smooth. The sides and upper surface are covered by
a coat of soldered grains, about 2 in the length of 1 mm. Among them
appear numerous small, smooth, slightly sunken, rounded, dark plates, usually
1.5 mm. in diameter; these begin near the tip, with a single plate on the
upper surface of each joint, and gradually increase in number towards the
base of the arm. The terminal twigs are encircled by double belts of hook-
bearing grains (Fig. 486), but the intervening spaces are not yet granulated.
Disk thick, rising well above arms; covered above by a soldered granulation
similar to that of the arm, with scattered smooth plates, which sometimes
are raised and sometimes sunken. Interbrachial spaces below covered by
a minute granulation, which is more or less obscured by skin, and seems
smooth to the naked eye. Radial shields not externally indicated. Genital
openings very large, extending from opposite the second tentacle-pit nearly.
to margin of disk, and capable of great distention; one of them was open to
the width of 9mm. The mouth-tentacles and first pair on the arm have no
tentacle-scales ; thence to margin of disk there are two or three, minute and
peg-like, to each tentacle ; for some distance beyond the margin each tentacle
has five small, thick, short, wide scales, about 1.5 mm. long, arranged in a
single line. Color in alcohol, uniform yellowish brown, with chocolate patches
where the smooth plates are.
Station 192, 129 fathoms, 1 specimen. .
The single specimen had lost one arm and a piece of the disk, the result
apparently of an injury, and not of self-division.
There was sent me recently a single Ophiuran of this Expedition, which has:
most singular arm-spines, like round-headed nails, or long-handled parasols.
They are arranged, not in one, but in several rows, thus forming an exception
to all other genera in the group. There is a similar species, but of quite a differ-
ent genus, in the collection of the second “ Blake” Expedition; and I propose
to prepare on these a separate paper.
MUSEUM OF COMPARATIVE ZOOLOGY.
DESCRIPTION OF PLATES.
PLATE XI.
Fig. 278. Amphiura maxima, below ; 3.
Fig. 279. sf $ above ; §.
Fig. 280. ne “ tentacle-scales ; 3.
Fig. 281. a ‘¢ _ arm-spines ; 3.
Fig. 282. “iy bellis, below ; 3.
Fig. 283. 7. ‘*.” above > 4.
Fig. 284. 4 ‘¢ arm-spines ; 3.
Fig. 285. aS incana, below ; 7.
Fig. 286. “ radial shields ; 4.
Fig. 287. Re “« arm-spines ; 4.
Fig. 288. By argentea, below ; &.
Fig. 289. Ay ih above ; $.
Fig. 290. ty si arm-spines ; &.
Fig. 291. ‘¢ _ joints near tip ; ¢.
Fig. 292. AF acacia, below ; 4.
Fig. 293. a: *¢ above ; 4.
Fig. 294. - ‘¢ arm-spines ; 2.
Fig. 295. constricta, below ; 4.
Fig. 296. af “) -above:s' f.
Fig. 297. “ i. arm-spines ; 4.
Fig. 298. : ” joints near tip of arm ; 4.
Fig. 299. me tomentosa, below ; 3.
Fig. 300. eo ri above ; 2.
Fig. 301. < i arm-spines ; 3.
Fig. 302. a tris, below ; 2.
Fig. 303. a *** above; §.
Fig. 304. . ** arm-spines ; 4.
Fig. 305. = lanceolata, below ; §.
Fig. 306. e above ; .
Fig. 307. a . arm-spines ; ¢.
Fig. 308. = glabra, below ; §.
Fig. 309. . “* above; §.
Eig. 310. ke ‘* arm-spines ; {.
Fig. 311. oe angularis, below ; +.
Fig. 312. br = above ; i.
Fig. 313. ot: bs arm-spines ; j.
Fig. 314. Py dilatata, below ; §.
Fig. 315. “ bs above ; §.
Fig. 316. i: Ge arm-spines ; 4.
=
1
BULLETIN OF THE
PLATE XII.
817. Amphiura concolor, below ; {.
318. ss ly above ; 4.
319. oe os arm-spines ; j.
320. es dalea, below ; %.
321. it: “above; 3.
322. ee ‘¢ arm-spines ; 3.
323. es cernua, below ; ¥.
324. Ss above; {.
325. a “© arm-spines ; {.
326. ‘ glauca, below ; 4.
327. 2. ss above; #¢-
328. - ** arm-spines ; 4.
329. * Verrilli, below ; 4.
330. ne “© above; $.
301. se ‘© arm-spines ; {-
332. = canescens, below ; 4.
333. i a above ; {.
304. e 7% arm-spines ; .
335. “ patula, below ; 4.
336. 2 id above ; 3.
337. sg “ — arm-joints ; 4.
338. Amphilepis patens, below ; $.
339. oe ‘above; 3.
340. ‘a « arm-spines ; ¢.
341. Ophiocnida pilosa, below ; }.
342. “above ; 4.
343. nf * — arm-spines ; {.
344. es scabra, below ; 4.
345. i ty above ; {.
346. x ‘© arm-spines ; 4.
PLATE XIlil.
347. Ophiactis flexuosa, below ; 4.
348. “ # above ; ¢-
349. ws . “ arm-spines ; f.
350. he nama, below ; 4.
351. “ “above ; 4.
352. sg « arm-spines ; 4.
353. e canotia, below ; ¢.
354. a ‘© above; 4-
355 ef «© arm-spines ; 4.
356. v poa, below ; {.
357. uf “© above; ¢.
358. 7 «© arm-spines ; §.
359. . cuspidata, below ; §-
ig. 360.
. 361.
. 362.
g. 363.
. 364.
. 365.
. 366.
. 867.
. 368.
. 369.
. 370.
. S71.
. 372.
5878.
. 374.
. 875.
. 376.
. 877.
. 378.
. 379.
. 380.
ee
. 382.
- 383.
, 884,
. B85.
. 386.
387.
. 388.
. 388
389.
. 390.
£291.
. 392.
. 393.
. 894.
. 895.
. 396.
. 397.
. 398.
. 399.
. 400.
. 401.
. 402,
. 403.
. 404,
MUSEUM OF COMPARATIVE ZOULOGY. 73
Ophiactis cuspidata, above ; 3.
ee is arm-spines ; 3.
“ resiliens, below ; ¢.
“ vis above ; j.
Si = arm-spines ; i.
2 hirta, below ; §.
ee ‘* above; %.
bh ‘* arm-spines ; {.
Ophiostiyma africanum, below ; 4°.
as above ; 42.
* _ arm-spines ; +2.
Ophiochondrus stelliger, below ; 2.
- ee above ; 2.
a “ arm-spines ; 4.
Ophiopholis japonica, below ; 3.
- “ - above ;)-6.
Re ‘* arm-joints, profile ; 3.
PLATE XIV.
Ophioconis pulverulenta, below ; 3.
<s o above ; #.
as e arm-spines ; #.
antartica, below ; $.
a e above ; 3.
“e ma arm-joints, profile; 4.
Ophiomyces grandis, below ; ¢.
+s ‘s above; #¢.
. ‘¢ arm-spines ; j.
me spathifer, below ; +?.
ae a above ; 42.
= i arm-spines ; 4.
5 a mouth-angle ; 42.
Pectinura heros, below ; 3.
a ‘s. above: 3:
6é 6é
arm-joint, profile ; 3.
arenosa, below ; 3.
ae te above; 3.
‘ a arm-joint, profile ; 3.
Ophiopeza aster, below ; 8.
de ‘¢ above; §.
arm-joints, profile; 3.
Ophiochiton lentus, below ; 8.
as s - above ; 4.
arm-joint, profile; §. :
Ophiothrix capillaris, below ; 3.
. _ above; 3.
arm-joints, profile ; 3
spine; 3.
66 66
Ce ce
ce ce
66 66
_
it BULLETIN OF THE
PLATE XV.
Fig. 405. Ophiacantha discotdea, below ; 3.
Fig. 406. - “ Prabovese5.
Fig. 407. ss di arm-spines 3 3.
Fig. 408. “ Valenciennest, below ; 3.
Fig. 409. r above ; 3.
Fig. 410. 4 - arm-spines ; #7. Some
they are really longer.
Fig. 411. Ophiacantha abnormis, below ;
Fig. 412. rs es
upper arm-plate omitted.
Fig. 413. Ophiacantha abnormis, arm-spines ;
above ;
2
of these spines broken:
2
i
i. Minute spines on outer edge of
i.
Fig. 414. re Normani, below ; 8.
Fig. 415. a % above ; 3.
Fig. 416. a fs arm-spines ; 4.
Fig. 417. Ophiothrix cespitosa, below ; 4.
Fig. 418. es ss above ; #.
Fig. 419. *§ spine ; +.
Fig. 420. “ fi arm-joint, profile ; 4.
Fig. 421. es aristulata, below ; 3.
Fig. 422. us + above ; 8.
Fig. 423. ig 3 arm-joint, profile ; 3.
Fig. 424. sh spine; i.
Fig. 425. 2g berberis, below ; 2.
Fig. 426. a above ; 2.
Fig. 427. a spine; 3.
Fig. 428. a os arm-joint, profile ; 7.
PLATE XVI.
Fig. 429. Amphilepis papyracea, below ; 1.
Fig. 430. es ¢ above ; i.
Fig. 431. “ wat arm-joints ; {.
Fig. 432. oe tenuis, below ; ¢.
Fig. 433. & ‘¢ - above ;. §.
Fig. 434. oe “ arm-joints ; 3.
Fig. 435. Ophiocreas carnosus, below ; t.
Fig. 436. * si above ; +.
Fig. 437. cs “ arm-joint near base of arm; +
Fig. 438. ve arm-joint near tip of arm ; f.
Fig. 439. s caudatus, below ; 4.
Fig. 440. * “ above ; 4.
Fig. 441. i se arm-joint near base of arm ; ?.
Fig. 442. mo = arm-joint near tip of arm ; 7.
Fig. 443. is wdipus, below ; j.
Fig. 444. oF © above 2d.
Fig. 445. i ‘¢ arm-joint near base of arm ; j.
Fig.
Fig.
fo}
Fig.
fo}
Fig.
" Fig.
Fig.
Fig.
Fig.
fo)
Fig.
Fig.
Fig.
Fig.
Fig.
Fig.
Fig.
Fig.
Fig.
Fig.
Fig.
Fig.
5
Fig.
Fig.
Fig.
Fig.
fo)
Fig.
Fig.
3
Fig.
Fig.
Fig.
Fig.
Fig.
Fig.
Fig.
Fig.
Fig.
Fig.
Fig.
Fig.
Fig.
Fig.
Fig.
MUSEUM OF COMPARATIVE ZOOLOGY. 75
446. Ophiocreas edipus, arm-joint near tip of arm ; 4.
447. Ophioglypha meridionalis, below ; 3.
448. ay a above ; §.
449, _ = arm-joints ; §.
PLATE XVII.
450. Astroschema tumidum, below ; 3.
451. 2 o above ; 4.
452. ie as arm-joint near base of arm; $.
453. oy = arm-joint near tip of arm; §.
454, ™ rubrum, below ; %.
455. . s above ; ?.
456. - = arm-joint near base of arm; j.
457. i ss arm-joint near tip of arm ; j.
458. - horridum, below ; ?.
459. if " above ; 3.
460. ” We near base of arm; 3.
461. _ = near tip of arm ; 7.
462. tf brachiatum, below ; 3.
463. = sf above ; }.
464. a - near base of arm; }.
465. - _ near tip of arm ; %.
466. se salix, below. Grains on sides of mouth-angles too large ; 3.
467. “s “¢ above; 2.
468. Me ‘¢ near base of arm ; ?.
469, se ‘¢ near tip of arm; 3.
470. Ophiocreas abyssicola, below ; 3.
471. “5 sy above ; 3.
472. am ee near base of arm; 3.
473. ne a near tip of arm ; 3.
Plate XVIII.
474. Astrotoma Murrayi, below ; 4.
475. es $s above ; +.
476. a $ arm-joints ; 4.
477. Astroceras pergiumena, below; %.
478. ss “ above; 2.
479. ne as near base of arm; 4.
480. “ - near tip of arm; 4.
481. Astroclon propugnatoris, below ; 4.
482. - Ad above ; 4.
483. ‘s ce profile ; 4.
484, “ Be near base of arm ; 4.
485. i i beyond Ist fork ; 4.
486. % - tip of twig ; 2. .
76 BULLETIN OF THE
Plate XIX.
a, mouth-shield; 8, side mouth-shield ; c, jaws; @, mouth-papille; d”, tooth-
papilla ; e, jaw-plate; %, under arm-plate; 7, side arm-plate; n, genital scale ;
o, genital plate ; g, tentacle-scales ; 7, tentacle; y, outer articulating prominence of
an arm-bone ; , inner articulating prominence of an arm-bone.
Fig. 487. Euryale asperum. Outer face of an arm-bone; y, articulating promi-
nence. %.
Fig. 488. 2. asperum. Inner face of next bone; 8, articulating prominence of the
“hour-glass” shape. 4.
Fig. 489. E. asperum. Widened outer face of an arm-bone at a fork; y, new
articulating prominence connecting with one new branch. 4.
Fig. 490. £. asperum. Inner face of next bone, split nearly in two, and bearing
two articulating prominences, 6. j.
Fig. 491. Astroschema oligactes. A joint of the arm near its end, with the skin split
to show the thick, squarish side arm-plate (z), with the broken pieces above, which
answer to upper arm-plates; the longer tentacle-scale, like a spine (q); and the
tentacle (7). 4.
Fig. 492. Astrophyton Agassizti. A portion of the mouth and under surface of the
disk in a very young specimen. .a, madreporic radial shield; 6, large side mouth-
shield; c, jaw; ad", tooth-papillee 3 ¢€, jaw-plate ; h, h, under arm-plate, divided in
three pieces; 7, large side arm-plates, meeting below; n, genital scale; 0, genital
plate ; g, tentacle-scales or arm-spines. +4°.
Fig. 498. A. Agassizii. Arm-joint near base of arm, showing the side arm-plate (¢)
and the spine-like tentacle-scales (q). 4.
Fig. 494. A. Agassizii. Joint of a twig near end of arm, in profile, to show the
side arm-plate (i) and the hooked tentacle-scale (g). Above is the characteristic
double belt of grains, each bearing a hook. 2.
Fig. 495. .A. Agassizii. Tip of a twig, showing the side arm-plates encireling the
arm, and bearing little hooks. 4/.
Fig. 496. Astrophyton Pourtalesii. Portion of under surface of disk, showing the
narrow arm characteristic of this section of the genus. 4.
Fig. 497. Astrophyton costosum. A portion of mouth and under side of disk, with
the skin removed to show the underlying hard parts; lettered like Fig. 492. 4.
Fig. 498. Astrophyton spinosum. Portion of under surface of disk, showing the
wide arm characteristic of this section of the genus. 3. :
Fig. 499. Euryale asperum. A part of mouth and surrounding parts with the
skin removed ; lettered as in Fig. 492. 4. .
Fig. 500. FE. asperum. Joints near tip of arm, to show transition from hook-like
tentacle-scales (q) to those of a stumpy shape. They are carried by the elongated
side arm-plates (i). Above is seen a large dorsal spine. ~ 7.
Fig. 501. E. asperum. Joint close to tip of arm, in profile, to show the
greatly elongated side arm-plate (2), bearing two hook-like tentacle-scales (¢). It
was this structure that Dr. Ludwig took for a pedicellaria.
MUSEUM OF COMPARATIVE ZOOLOGY. ine
INDEX
TO SPECIES OF OPHIURIDA AND ASTROPHYTID.
Described by the author from the dredgings by L. F. de Pourtales on the U. S. Coast Sur-
vey, and those of the “ Hassler,” ‘‘ Blake,” and ‘‘ Challenger” Expeditions, published
in the Illustrated Catalogue and the Bulletin of the Museum of Comparative Zoology.
Amphilepis
papyracea. Bulletin, VI. 2, p. 34.
patens. = of p- 34.
tenuis. a 7 p. 35.
Amphiura
acacia. Bulletin, VI. 2, p. 21. :
angularis. ‘ “Dp. Sa
anomala. Illustrated Catalogue, VIII. 2, p. 15.
argentea. Bulletin, VI. 2, p. 21.
Barbare. Illustrated Catalogue, VIII, 2, p. 17.
bellis. Bulletin, VI. 2, p. 19.
canescens. ne op SR
cernua. me iy. pea: ~ 2
concolor. m eS Gt ee
constricta. *¢ fer peas
cuneata. aa V9, p.. 225.
dalea. VI. 2, per.
dilatata. o oP
duplicata. Illustr. Catalogue, VIII, 2, p. 19; Bulletin, VI. 2, p. 31.
glabra. Bulletin, VI. 2, p. 25.
glauca. v7 hae ao
grandisquama. I. 10, p.. 334.
incana. re VI.. 2, pera.
wis. i AA) peenoens
lanceolata. ¢ fe: ht BAe
lunarts. V..9, p. 226.
maxima. a VI.22, ps 19.
patula. 5 "pe ak
pulchella. “4 I. 10, p. 337.
repens. Illustrated Catalogue, VIII. 2, p. 81.
78 BULLETIN OF THE
Amphiura
semiermis. Bulletin, I. 10, p. 332.
tomentosa. a VI..2,; pe®.
tumida. : ¥. 9} :p. 225.
Verrilli. as VIL.2. pee,
Astroceras
pergamena. Bulletin, VI. 2, p. 62.
Astroclon
propugnatoris. Bulletin, VI. 2, p. 69.
Astrocnida
isidis. Ann. des Sc. Nat., 5 ser., Vol. XVI., Art. 4, p. 1.
Astrogomphus
-vallatus. Bulletin, [. 10, p. 350.
Astrophyton
mucronatum. Bulletin, I. 10, p. 348.
Pourtalesw. Illustrated Catalogue, VITI. 2, p. 28.
spinosum. a cs aS ictt pereed.
Astroschema
arenosum. Bulletin, V. 9, p. 235.
brachiatum. “ VL. 2, p. G7.
horridum. = arm 1
intectum. tc V9, p. 235:
leve. Illustrated Catalogue, VIII. 2, p. 26.
rubrum. Bulletin, VI. 2, p. 68.
salix. o 2p. 66.
tenue. Illustrated Catalogue, VIII. 2, p. 27.
tumidum. Bulletin, VI. 2, p. 68.
Astrotoma
Agassiz. Tlustrated Catalogue, VIII. 2, p. 24.
Murrayt. Bulletin, VI. 2, p. 61.
Ophiacantha
abnormis. Bulletin, VI. 2, p. 59.
aspera. " V.9, p. 228.
cornuta. + V. 7, p. 145.
cosmica. " * p. d46:
cuspidata. i oo peas:
discordea. VI. 2, p. 57.
echinulata. x V.9) po 228.
granulosa. Mf Ved, pf:
hirsuta. Mlustrated Catalogue, VIII. 2, p. 12.
imago. Bulletin, V. 7, p. 139.
levispina. vp. VaR
longidens. ‘ ‘fp. 144.
marsupialis. Illustrated Catalogue, VIII. 2, p. 13.
nodosa. Bulletin, V. 7, p. 144.
MUSEUM OF COMPARATIVE ZOOLOGY.
-Ophiacantha
Norman. Bulletin, VI. 2, p. 58.
rosea. e We Sp. teas
scutata. 7 V..9, p.-220.
segesta. “ ¥. espe Pe
sentosa. a fp. 140.
serrata. " * opr tae:
sertata. a F.. 10,' p. 326.
stellata. Tllustrated Catalogue, VIII. 2, p. 11.
stimulea. Bulletin, V. 7, p. 141.
Troscheli. ea. ire,
tuberculosa. ‘* Oe ea
Valenciennesi. ‘ VI.-2; p. oF.
vepratica. “y V. 7, pi tes.
Ophiactis
canotia. Bulletin, VI. 2, p. 40.
cuspidata. ‘ ‘<p 38.
flexuosa. cs SS rane
hirta. ri Gee
humilis. 5 I. 10, p. 329.
loricata. 3 <p: gal.
nama. 3 VL & p. 33.
plana. a I. 10, p. 330.
poa. a VE. 2, p. 40.
resiliens. es ey Pi eae,
Ophiernus
vallincola.” Bulletin, V. 7, p. 122.
Ophiobyrsa
rudis. Bulletin, V. 7, p. 132.
Ophiocamax
hystrix. Bulletin, V. 9, p. 282.
vitrea. “a V. 7, p. 156.
Ophioceramis
albida. Illustrated Catalogue, VIII. 2, p. 10.
(?) clausa. Bulletin, V. 7, p. 124.
(?) obstricta. a <p. 124.
Ophiochiton
fastigatus. Bulletin, V. 7, p. 182.
lentus. € VI. 11, p. 55.
Ophiochceta
(?) mixta. Bulletin, V. 9, p. 222.
Ophiochondrus -
convolutus. Bulletin, I. 10, p. 328.
stelliger. om VIL, peed
80 BULLETIN OF THE
Ophiocnida
abnormis. Bulletin, V. 9, p. 227.
filograma. lustrated Catalogue, VIII. 2, p. 20.
olivacea. Bulletin, I. 10, p. 340.
pilosa. VI. 2, p..32.
scabra. ay spo:
Ophiocoma
papillosa. Ilustrated Catalogue, VIII. 2, p. 11.
Ophioconis
antarctica. Bulletin, VI. 2, p. 44.
miliarva. 7. V9, pare
pulverulenta. VI. 2, p. 45.
Ophiocreas
abyssicola. Bulletin, VI. 2, p. 64.
carnosus. a eo Sp. ‘6a.
caudatus. ., oe pGa:
lumbricus. - I. 10, p. 347.
cedipus. , V1.2, p-63..
Ophiocten
amitinum. Bulletin, V. 7, p. 100.
depressum. a I. 10, p. 20.
hastatum. is V.@,"p. 103.
pallidum. C 4S GEO.
umbraticum. * spe (re | 8
Ophiogeron
edentulus. Bulletin, V. 7, p. 161.
Ophioglypha
acervata. Bulletin, I. 10, p. 316.
a@qualis. Vu, pee
albata. 5 sles er a’
ambigua. re pete.
brevispina? E. A. Smith, Bulletin, V. 7, p. 78.
confragosa. Bulletin, V. 7, p. 97.
a3
6c
convera. p. 84.
costata. ‘ “yp. 40,
Deshayesi. - shea 5) 57
elevata. : " pEBe:
Saleifera. oT 10 poe,
ferruginea. So VO oe
Jlagellata. ee ‘o apnGa.
fraterna. 4 fe) vay aes
umbecillis. c «pets.
imermis. - ae aS
imornata. : <a
intorta. ” *) SpS:
MUSEUM OF COMPARATIVE ZOOLOGY.
Ophioglypha
irrorata. Bulletin, V. 7, p. 73.
jeyuna. a ae? pt Bt
Lacazet. 3 ars” | es
lapidaria. “ ‘c _ p«:803
lepida. as poet
lenosa. oy OPS Deas
Ljungman. .“ o ~ pel:
Loven. 93 eo pASe
meridionalis. ‘ VI. 2, p..56.
minuta. o V. 7, p. 94.
orbiculata. ‘ «pes.
ornata. ch pp. 86.
palliata. 5 o paee:
ponderosa. ‘' “pegs:
radiata. a pees
rugosa. si ey poe
sculptilis. “ “ “p. 84
solida. 4 SS ip Ee
undata. - ©) pow
undulata. ‘ i Pe
variabilis. * | Be So
Ophiolebes
scorteus. Bulletin, V. 7, p. 158.
vestitus. “<p. 159:
Ophiolipus
Agassiz. Bulletin, V. 9, p. 220.
Ophiomastus
secundus. Bulletin, V. 9, p. 218.
tegulitius. “ V. 7, p. 104.
Ophiomitra
carduus. Bulletin, V. 7, p. 154.
cervicornis. Illustrated Catalogue, VIII. 2, p. 14.
chelys. Bulletin, V. 7, p. 152.
diupsacos. cs ep. Too.
exigua. Ae ¥..9, p. 221.
plicata. si V. 7, p. 150.
Sars. s sp. Loy,
valida. 110, :p, 825.
Ophiomusium
acuferum. Illustrated Catalogue, VIII. 2, p. 7.
armigerum. Bulletin, V. 7, p. 109.
cancellatum. a bites 3 a
cortucosum. “ ar ae a,
eburneum. ee i 80; peer.
VOL. VI. —NO. 2. 6
89 BULLETIN OF THE
Ophiomusium
flabellum. Bulletin, V. 7, p. 120.
granosum. pee:
laqueatum. fo op SS,
lunare. ) pe ae.
Liitken. ¢ pe.
planum. ss V. 9, p. 218.
scalare. si Not, ps LER
serratum. a “fp. 109.
simplex. tr mt op. QUBD:
testudo. Illustrated Catalogue, VIII. 2, p. 8.
Ophiomyces )
Srutectosus. Bulletin, I. 10, p. 345.
grandis. VI. 2, p. 46.
mirabilis. y I. 10, p. 343.
spathifer. Ry Vi 2a.
Ophiopeza
aster. Bulletin, VI. 2, p. 50.
Petersi. = VO, pp. 205
Ophiopholis
japonica. Bulletin, VI. 2, p. 42.
Ophiophyllum
petilum. Bulletin, V. 7, p. 130.
Ophioplax
Ljungmani. Mlustrated Catalogue, VIII. 2, p. 22.
Ophioplinthus f
grisea. Bulletin, V. 7, p. 106.
medusa. i = pS:
Ophiopsila
fulva. Bulletin, V. 9, p. 227.
Ophiopyren
brevispinus. Bulletin, V. 7, p. 183.
longispinus. MS cr pe Ast
Ophiopyrgus
Wyville Thomsont. Bulletin, V. 7, p. 121.
Ophiosciasma
attenuatum. Bulletin, V. 7, p. 160.
Ophioscolex
dentatus. Bulletin, V.7, p.157. |
Stimpsonii. Mlustrated Catalogue, VIII. 2, p. 28.
tropicus. Bulletin, V. 7, p. 157.
Ophiostigma
africanum. Bulletin, VI. 2, p. 41.
Ophiothamnus
remotus. Bulletin, V. 7, p. 149.
vicarius. “ss I. 10, p. 342.
MUSEUM OF COMPARATIVE ZOOLOGY.
Ophiothrix
aristulata. Bulletin, VI. 2, p. 50.
berberis. ” OF Dy (oe
cespitosa. " A Pe
capillaris. a . pol.
Ophiotrochus
panniculus. Bulletin, V. 7, p. 129.
Ophiozona
antillarum. Bulletin, V. 7, p. 127.
depressa. rs i pe l2s.
dubia. V.9, p.. 224.
insularia. Vid, pe ie.
nivea. Illustrated Catalogue, VIIL. 2, p. 9.
stellata. Bulletin, V. 7, p. 125.
tessellata. hy VoD py Bes,
Pectinura
arenosa. Bulletin, VI. 2, p. 48.
heros. a op. ae
Sigsbeia
murrhind. Bulletin, V. 9, p. 234.
hoe.”
.
< -
ral ef oe "} Pa |
bee \ 1
Zoe
HELV".
05
oe @,
és,
<@
VA
e
-_
ny) \ rs
NY mi
2 Wh,
CS
~S
XY
y
RS
N QW
Sy
SW) a
SS
Piateée XI
TT,.aé nat.
sy
Ny
DY
y
oes
K aih. feingson ao nat
Ca
CX xX dy
TSU
.@. or P
eh 7
SIN
IMO 9
IPRS SF
Ss
ERS
LYS
SS
1s" ars aS
C/ LSPS
AO,
Sate Xi
,
A 4
Wel
my
‘/. ve ) ie
7 at a)
Pyrat
ry pe Wer
‘ 1 ,
aS hae
Ze a =
Nt
mi Hi
\
\\ 4Yln
\ \ +
——— SaIITING GO. 220 DEVONSHIRE ST. BOsTON ci Z XV
| Tap HELIOTYPE PRINTING CO. 22 Sta £
? THE HELIOTYPE PRINTING CO. 220 DEVONSHIRE ST. Boston sae :
KP ad net © HELIOTYPE PRINTIN ) DEVONSHIRE Sr. B 7 Pale XVI
we. le
=bad x Jy
VONSHIRE St
3
>}
>
Y
J
Ss
6
co
TING
SLIOTYPE PRIN
HE HE
7
a
()
a0 Ra
A
THE HEMOTYPE PRIN
oa ee
SRINTINGCO. 220 DEVONSHIRE 31 I ) iy y
¢ XV/L
GCECE
4
ead!
2 a _
‘e
iat
i
ieee
faa
Pah se
eee
Ss
f..
ee
= k es 5
| Oe ee dk De
- : he 5 i aT ; a ,, Sa wr
au iva ’ 7 rn re aa _
pe ae
— =
we eras
— = vee
~
+
&
u ‘
5 & r
i
; 2 y EAP at
. :
, ye i
a i 7 -
' aol
| -,; ,
” 7 ry,
| < , eng
. 5 pp = \
v j ’
ui pel d , i
P ' ° “4 i
| j a va 7 ; \
: 1 S Pyar : vad
. i;
‘ nye ; and
P ° nl « fi ’
fs
A
4
Trp Perradn Soom OA fon Tr f
J So . mld nat. LHE HELIOTYPE PRINTINGCO. 220 DevonsHie Sr. Bosrott
Sate XIX
By ay rey gage) ik OAS ant RN: ba
- e Yn rey Ae, i * pC a e 2
; ¥ aaa i ay eae ian . a em ams he 3 ah hone Asal
. ) i
: 4 ’ : ; Hast oan |
‘ | +9; ;
a, ° " =) r aoa :
> a 1 be Te a * ®
> : " » @ 1 5 nd ~
a
>
: \
ia
4 7 . ad _ -
- Wan #. 6 a 3 &
i ; pe i D 6 Ge
_ = 7 7 5
4 y aoe
, Le -
; ; 7
i ; ’ ‘ «
ne -
) 4 7 »
= 7
; oth . ,
Pu
.
3
>=
we
<>
.
a
a
:
_
-
+
7
4
Eee
a!
7
-
:
i \ n Oi] .
’
7
: -
a
> ive
7 fe \ TY <> a a
i :
: &
J 2 e
—— +
ic ii
7
= 1 " a ; :
a f, Me
7 id = a 7 F he
: ey ae el
‘
i. J
i
’ = al
P %
*& ~ }
: a y) .
= ‘
7 ‘
1
1
f i
a. : | ae
‘ a 7
74 = ,
¥ >
he ’ 4
a L -
; FA
; ‘ ¥
No. 3. — Reports on the Results of Dredging, under the Supervision
of ALEXANDER AGassiZ, in the Gulf of Mexico, 1877-78, by the
United States Coast Survey Steamer “ Blake,’ LIEUTENANT-CoM-
MANDER C. D. SiGsBEE, U. 8S. N., Commanding.
(Published by permission of CARLILE P. PaTTErson, Supt. U. 8. Coast Survey.)
NG
General Conclusions from a Preliminary Examination of the Mollusca,
by W. H. Dat.
THE collection made by Mr. Agassiz and Lieut.-Com. Sigsbee on
board the ‘‘ Blake” contained about five hundred species, from which
the Pteropods and some other groups have been excluded, as will be
seen by the tables, leaving 462 species to be considered in this paper.
Of course the specific determination of all these forms is a task which
must necessarily occupy a large amount of time and labor, and if that
had been a necessary preliminary to a report of any kind I should have
nothing to say on the subject at the present time. Fortunately, how-
ever, the generic affiliations can be approximately determined almost at
sight, and species may be almost as readily separated from one another
by a practiced eye; so that it is not necessary to wait for the comple-
tion of the drudgery of researches into the nomenclature of the various
specific forms before announcing any general conclusions.
Before proceeding to these it is necessary to make a few preliminary
statements.
I. The observations herein tabulated are not to be taken as exact in
every instance. The limits of a species, or the reference to a subordi-
nate generic group, is liable to be modified, occasionally, by more mature
study. The examination of the collections for 1878-79, made under
the supervision of Mr. Agassiz on board the “Blake,” will doubtless
add to, and in some instances change, the figures deduced from the col-
lections of the previous season; all that is claimed for the conclusions
here put forward is, that the general character of them seems already to
be sufficiently established by the evidence in hand.
VOL. VI. —NO. 3. a
86 BULLETIN OF THE
If. The combination of sundry shoaler-water collections, made by
Pourtales and Agassiz on the Coast Survey steamers “ Bibb” and
‘‘ Hassler,” with the deep-sea dredgings, has proved of the highest im-
portance, by completing the evidence in several cases where the absence
of material from shoal water would have rendered a suspension of judg-
ment necessary.
III. In several cases where the presence of dead shells in the deep-
water material was the only evidence of the presence of a shoal-water
species there, its living presence has not been taken as proved unless
the multiplication of instances and graduation of depths confirmed the
supposition. Ifa too great conservatism has been exercised in this way,
it is on the side of safety in the generalizations. The names provision-
ally adopted in the tables are of a conservative character as regards
their limits ; since, in this way, a more just comparison with the lists
of authors like D’Orbigny and C. B. Adams is rendered possible ; and
this course is also less likely to result in errors of determination due
to insufficient study. '
IV. The absence of any tolerably complete catalogue of West Indian
mollusks in accessible shape has interfered with carrying the comparisons
as far as might have been desired. The best that could be done was ta
compare the lists of C. B. Adams’s Jamaican shells and those described
in D’Orbigny and Sagra’s Mollusca of Cuba, to eliminate identical species,
and to assume that the resulting list bore about such a proportion to
the whole litoral molluscan fauna of the West Indies as the “ Blake”
dredgings do toward the whole abyssal fauna. Upon this assumption,
however, though so convenient for a brief comparison, no very impor-
tant conclusions are based. As the shells quoted by the above-men-
tioned authors were all (or nearly all) obtained in the limits of the
shore fauna, they afforded a better means of comparing that faunal re-
gion with the abyssal region than more modern and complete lists like
that of the shells of Guadaloupe (Crosse and Fischer), which contains
many true deep-water species brought up on fishing-lines or by coral-
hunters.
The following are the most interesting and important deductions
which seem to result from the facts before me.
I. The facts, already known, that certain species of mollusks have a
very limited vertical range, forming respectively a litoral and an abyssal
fauna, are supplemented by the additional hitherto unrecognized fact
that a fair proportion (say 20 per cent in the present case) have a verti-
cal range which extends from the true litoral region (less than 50
MUSEUM OF COMPARATIVE ZOOLOGY. 87
fathoms) to the depths of the abyssal region (250 to 2,000 fathoms) un-
limited by temperatures actually encountered.
II. Of the species with great vertical range (from less than 100 to
more than 500 fathoms), the smallest part (ten per cent) are of groups
which have been regarded as belonging to or characteristic of the shores
of cold or boreal areas. The next larger part (twenty per cent) belong
to. groups hitherto considered characteristic of shoaler warm or tropical
waters, while more than sixty per cent belong to groups not especially
characteristic of the litorale of either region.
III. Of the species found in the abyssal fauna without regard to
their vertical range above it, ten per cent may be termed boreal, thir-
teen per cent tropical, and more than seventy-five per cent uncharacter-
istic forms.
IV. Since the tropical forms belong to the same groups as those char-
acteristic of the local litoral mollusk fauna, it is eminently probable that
the abyssalregions have local faunz proper to their various portions, and
that a universal exclusive abyssal fauna, so far as mollusks are concerned,
does not exist. This must be qualified by the admission of the exist-
ence in the abysses (as well as on the ltorale) of ubiquitous species-
forms ; which, however, do not form a universal abyssal fauna, any more
than Mytilus edulis, Saxicava rugosa, and Poronia rubra form a universal
litoral fauna. The local nature of different portions of the abyssal fauna
is also confirmed by the distinctness of the Challenger mollusks from
those of the Blake, but a very small number appearing identical as far
as a cursory examination could determine.
There can be no doubt that the uniformity of generally low tempera-
tures (and consequently of food) affords special facilities for the wide dis-
tribution of boreal forms through the abyssal region. But where adjacent
shores can (by washing and sinking) afford a different or greater variety
of food without too excessive temperatures, local abyssal faunz will prob-
ably always be developed, and with characteristics assimilated to those
of the litoral fauna of the same part of the earth’s surface. The present
collection shows conclusively that a difference in pressure of some 120
atmospheres and in temperature of 41.5 degrees has been sustained by
different individuals of the same species without perceptible change in
the external appearance of their hard parts or shells.
V. The specific characters of many of the strictly abyssal species ap-
pear to exhibit a very remarkable degree of variation within supposed
specific limits, although it would seem as if the conditions under which
they live must be remarkably uniform. This would indicate that the
88 BULLETIN OF THE
tendency to variation is less dependent upon changes in the existing
environment than has generally been assumed.
The total number of litoral species recorded by Adams and D’Orbigny,
throwing out those groups, like the Pteropods, not germane to the
inquiry, is 580, as compared: with 461 collected by the Blake. The
number of genera represented by the former is about 110, while some
98 genera are found in the Blake collection. The 461 species included
in the last-mentioned collection comprise 210 which are litoral or do not
reach great depths, while 251 are abyssal or ubiquitous. These numbers
are of course approximate, and subject to correction, but probably not
seriously in error.
Out of 48 species, of 44 genera, having great vertical range, 24 have a
range of 500 to 750 fathoms; 17 have a range of from 750 to 1,000
fathoms ; and 7 have a range of from 1,000 to 1,555 fathoms. Bearing
in mind that the absolute depth of the extreme range may be much
greater than this, the astonishing fact is evident that the same species
may experience a difference, between two of its stations, of the weight of
nearly two miles of sea-water. The possibility of this of course lies in
the permeation of the soft parts by the sea-water, thus equalizing the
pressure. It is almost certain, however, that individuals from the great
depths would die if removed to shoaler water, unless by extremely slow
degrees.
It is noticeable among the deep-sea forms that the sculpture tends to
be slight, the shell thin, pale or colorless, and in the spiral shells there
is a tendency to a knobbing or denticulation of the posterior edge of the
whorls at the suture. To each of these peculiarities there are, however,
conspicuous exceptions.
The following tables exhibit in detail the statistics from which the
foregoing conclusions have been drawn.
MUSEUM OF COMPARATIVE ZOOLOGY, 89
COMPARATIVE TABLE OF THE LITORAL AND ABYSSAL
WEST INDIAN AND GULF FAUNA.
|
( CONT SO) Or CO DD
D’Orb. Vertical range
and Blake. of genus in
Group or genus, |C-B.Ad. fathoms. eee STE CHES:
Oe S| est
———EE —__
SC — | — ——— —_—<—<$<$_$_____ | —______
Species belong- | Range of single
Anatinide 1 7 15 640 5 2 2 640
Ancillaria 1 0
Anomia 2 0
Area 15 6 13 | 1568 3 3 310 | 1568
Astyris (Columb. 3 220 805 0 3 220 450
Avicula 3 0
Bulla 17 4 87 | 1568 1 3 100 | 1568
Cadulus 0 6 30 | 1002 0 6 100 | 1002
Calyptreea 1 1 95 | 100 1 0 95 | 100
Cancellaria g 1 54 84 1 0 54 84
Cardita 2 6 1 8) 640 3 3 2 640
Cardium 10 9 30 187 7 2 30 182
Cassis 4 0
Cerithiopsis 20 11 50 | 1002 2 9 100 | 1002
Cerithium 0
Chama 2 1 80 100 1 0 80 100
Chitonide 12 1 128 2 0 i
Cistella 0 9 80 805 0 9 30 805
Columbella 16 ‘| (Astyris.)
Conus 4 S 19 100 3 0 19 100
Corbula 5 10 4g | s05| 5 5 le
100 640
Crania 0 1 105 116 1? 105 116
Crassatella 0 1 30 2 1 0
Crepidula 2 1 2 539 0 1
Crucibulum 0 1 54 128 i 0 54 128
Cylichna 3 100 | 640 1 2
Cyprea 6 0
Cypricardia 1
Dentalium 3 9 50 , 1568 2 Z 50 | 1002
Dolium 2
Donax 4
Erato 1
Erycina 1
Eudesia 1 100 310 0 1 100 310
Eulima 4 10 100 640 6 4
‘Fasciolaria 2 3 54 292 2 1 220 292
Fissurellidee
a. Puncturella ) ( 2 100 | 640 0 2 100 | 640
b. Glyphis lid | 3 50 | 805 1 2 100 | 805
c. Fissurella 1 13 | 805 0 1 13 | 805
d. Fissurellidea | } 1 100 2 1 0
e. Emarginula 2 3 80 | 640 0 3 100 | 640
Fusus 3 5 15 | 1002 3 = 15>} 1002
Galerus 1 1 2 640 0 1
Gastrochena 2
Gouldia 2 3 13 | 1568 0 3 13..\ 1568
Hipponyx 3 1 229 2 0 1
Leda 2 4 54 | 1568 0 4 54 | 1002
90 BULLETIN OF THE
ae Blake. ih aren Species belong- | Range of single
Group or genus. C B.Ad. fathoms. mg to the species.
No. sp. | No. sp. |} From To Litor. | Abyss. | From To
48 | Leptothyra 2 15 | 1002 i 1 15 | 1002
49 | Lima 6 19 640 3 3 19 287
50 | Limopsis 2 13 | 1568 0 g 30 | 1568
51 | Liotia 1 2 80 220 a x
52 | Lithodomus 4
53 | Litorina 7
54 | Lucinide 15 12 19 805 8 4 19 640
55 | Lutraria 3
56 | Lyonsia 1 2 |» 95.) 1920 1 37 2 1920
57 | Mactra 2
58 | Margarita 6 80 | 1568 0 6 80 | 1568
59 | Marginella 17 13 54 } 1002 8 5 54 | 1002
60 | Mitra 6 4 84 119 4 0 4
61 | Modiola 9 1 220 339 0 a
62 | Modiolaria 2 339 640 0 2
63 | Monodonta 5 1 of 220 1 0
64 | Murex 7 5 54 640 1 4 54 640
65 | Narica 3
66 | Nassa 13 3) 13 640 2 1 13 640
67 | Natica 7 4 14 640 2 g
68 | Newra 10 54 | 1002 5 5 84 229
69 | Nerita 6 ;
70 | Neritina 7
71 | Nucula 3 30 640 0 3 30 640
72 | Nuculocardia if
73 | Odostomia Oe
74 | Oliva 6 1 54 2 1 0
75 | Olivancillaria a
76 | Olivella 6 4 72 805 0 4 127 805
77. | Oniscia 2
78 | Orbicula 1
79 | Ostrea 4
80 | Ovula 2 2 12 80 2 0
81 | Patella if ;
82 | Pecten 4 9 13 805 8 1 13 805
83 | Pectunculus 5 2 54 888 1 1 54 888
84 | Pedicularia 1 100 640 0 ] 100 640
85 | Perna 5
86 | Petricola 2
87 | Phasianella 4 1 287 ? 0 1g
88 | Pholas 6
89 | Pinna 4
90 | Planaxis 3
91 | Platidia 1 ||.2120 || 292 10 1 | 120] 292
92 | Pleurotomaria 2 69 | 200 if 1?
Plewurotomide i
93 | a. Bela | bs 3 | 3391 805| 0 3. |) 4988 isge
94 | b. Drillia, etc. 108 15 | 1568 57 51 100 805
95 | Plicatula 1 2 36 54 2 0
96 | Psammobia 4
97 | Purpura 12 .
98 | Pyramidella ik 1 84 |. 100 1 0
99 | Pyrula 2
100 | Ranella 4
MUSEUM OF COMPARATIVE ZOOLOGY.
Vertical range
of genus in
Species belong-
91
Range of single
ee | ef | |
————
Ringicula
Rissoa
Rissoina
Rotella
Sanguinolaria
Scaphander
Scalaria
Semele
Seguenzia
Sigaretus
Siliquaria
Solarium
Solecurtus
Solen
Solenella
Sphenia
Spondylus
Stomatia
Strombus
Tellinides
Terebra
‘Terebratula
Terebratulina
Teredo
Thecidium
Tornatella
Trichotropis
Triforis
Tritonium
Trivia
Trochidee
a. Gibbula
b. Calliostoma
Turbinella
Turbo
Turbonilla
Turritella
Typhis
Utriculus
Veneridz
Vermetus
Verticordia
Vitrinella
Volvula
Voluta
Waldheimia
(see Eudesia)
Xenophora
Yoldia
Totals
and | Blake
C.B.A
No. sp. | No. sp.
1 1
10 6
6
5
2
0 1
9 ne
4 2
0 1
3 -
0 2
5 3
3
1
0 1
3
2
1
6
27 13
2 4
0 1
0 1
1
0 2
1 4
0 1
0 2
10 }
& 6
3
Te
7
9
10 5
2 4
0 3
0 1
18 17
3 6
1 5
0 3
0 1
1
1 2
0 3
| 580 | 462
fathoms.
From To
339 640
100 640
54 220
15 805
30 U7
292 2
84 2
80 805
80 805
118 2
13 860
14 640
100 300
30 805
100
111 805
84 2
80 175
100 2
80 805
54 805
37 805
50 640
14 640
127%.) 1002
100 450
30 805
37 805
84 310
640 805
100 2
36 229
182 | 1568
ing to the
Litor. | Abyss.
0 1
3 3
0 1
4 3
2 0
0 1
1 0
1 1
0 3
1 0
5 8
3 1
0 1
0 1
0 2
0 4
1 0
1 1
1 0
i 5
0 3
0 9
3 2
2 2
0 3
0 1
14 3
3 3
2 3
0 3
1 0
1? 1
0 3
211 251
species.
From To
339 640
#2 805 ?
80 805
80 805
30 805
100 300
30 805
TEL 805
80 805
54 805
70 805
127 | 1002
100 450
84 287
37 805
100 310
36 229
182 | 1568
BULLETIN OF THE
te)
bo
Illustrations of the Range of individual species in Depth.
(x, boreal forms ; 0, tropical forms ; n, uncharacteristic forms.)
o Arca, 100, 220, 310, 450, 480 fms.
o ““ (another sp.) 310, 1568 fms.
n Bulla, 100, 450, 533, 568, 640, 805, 1568 fms.
‘Cadulus, 100, 31, 805, 1002 fms.
Cerithiopsis, 100, 640, 805, 1002 fms.
n 4 (another sp.) 50, 85, 94, 100, 450, 805 fms.
n Cistella, 30, 43, 80, 100, 101, 200, 220, 250, 450, 640, 805 fms.
» Corbula, 100, 640 fms.
=) “ (another sp.) 48, 72, 100; 127, 450, 805 fms.
n Dentalium, 50, 80, 84, 100, 101, 119, 175, 200, 539, 640, 888, 1002 fms.
= 38
n $ (another sp.) 339, 539, 640, 805, 860, 1568 fms.
n Eudesia, 110, 119, 125, 175, 200, 229, 310 fms.
Fissurellide.
x Puncturella, 100, 220, 640 fms.
nm Glyphis, 100, 287, 805 fms.
n Fissurella, 13, 50, 80, 72, 127, 640, 805 fms.
n Emarginula, 100, 287, 292, 310, 640 fms.
nm Fusus, 15, 54, 125, 128, 152, 229, 1002 fms.
n Gouldia, 13, 84, 310, 1568 fms.
n Leda, 54, 75, 80, 100, 190, 220, 287, 310, 640, 1002 fms.
a Limopsis, 30, 84, 100, 119, 220, 292, 310, 447, 450, 480, 539, 640, 805,
1568 fms.
m Lucina, 19, 84, 640 fms.
x Margarita, 100, 177, 220, 287, 331, 450, 539, 640, 805, 860, 888 fms.
x ée (another sp.) 80, 119, 310, 1568 fms.
o Marginella, 54, 70, 72, 80, 100, 111, 125, 152, 229, 640, 805, 1002 fms.
o Murex, 54, 640 fms.
n Nassa, 13, 72, 80, 100, 177, 640 fms.
n Neera, 84, 152, 229 fms.
n Nucula, 30, 84, 100, 158, 182, 220, 310, 539, 640 fms.
o Olivella, 127, 177, 805 fms.
n Pecten, 13, 30, 100, 119, 127, 229, 243, 287, 292, 310, 381, 424, 450, 480,
539, 640, 804, 805 fms.
m Pectunculus, 54, 68, 80, 84, 95, 119, 888 fms.
nm Pedicularia, 100, 450, 640 fms., on Gorgoniz and corals,
Pleurotomde.
xz Bela, 413, 447, 640, 805 fms.
o Candelabrum, 100, 640, 805 fms.
o Ringicula, 339, 447, 640 fms.
MUSEUM OF COMPARATIVE ZOOLOGY. 93
o Siliquaria, 80, 100, 127, 220, 450, 805 fms.
o Solariide, (sp.) 101, 119, 128, 292 fms.
0 : (another sp.) 80 - 805 fms.
n Tellina, 30, 54, 72, 80, 84, 111, 229, 805 fms.
n Terebratula, 100, 101, 119, 175, 270, 292 fms.
n Terebratulina, 30, 80, 100, 101, 115, 119, 127, 220, 240, 270, 292, 450, 471,
539, 640, 805 fms.
nm Fornatella, 111, 310, 450, 805 fms.
o Trivia, 100, 119, 287, 640 fms.
o “ (another sp.) 80, 175, 805 fms.
o “ (another sp.) 80, 177, 640, 805 fms.
Trochide.
n Gibbula, 54, 80, 100, 220, 805 fms.
n Calliostoma, 70, 80, 100, 128, 805 fms.
o Typhis, 127, 158, 182, 175, 1002 fms.
nm Utriculus, 100, 220, 450 fms.
n Vermetus, 37, 80, 95, 100, 805 fms.
x Yoldia, 182, 190, 450, 805, 1568 fms.
Ten distinctively tropical genera with fourteen species.
Five distinctively arctic genera with six species.
Twenty-eight uncharacteristic (or generally temperate-region) genera with
thirty-one species.
Total species ranging from litoral to abyssal fauna, and which may be con-
fidently quoted, fifty-one, of forty-three genera,
FEBRUARY 5, 1880.
Hey ane ed oe ea Ted
Mera oe ve Oe bhai ,
A 1/0 MORN eee i 7
sree! i eT din! ACU 1) ae ls,
i RUT een y hs a) hea) gt v
eV ee Ane
Pe Ma ae wh t
2) ap
i es eee ee 3
a foe OE Oa Se |
PT tA elie nh ys. ie reat |
ETN COP BNE OE ORE. oe ae:
it 1 ly ¥
. ] ‘
ae 7 ee | i rs! Me lh Peo aut tne ay ne
ee wee nara”
a, aa, a en ad st Me be a
vi 45, /' ‘ * , _ ; ‘ 5 Ah a pe
ets Pe ES" iene aa Per an or ie ae
fe ene chert SSID
ion ys | ts yi eee ein “it it ae
CT Se ee Oe
Le sia agi dow eng pe gi ia eanae ‘
st 2 le ee pee Aa hed eortiet ope Pips as
ai yates CeoneePRCRNE is) ani ee) ik bts a bh ‘oh
i 29 les it Siac Feat ait, nk
sahil Hels mast at he inal
7 1
3 ‘ ' ;
‘ f ii i
é A we . ) F \
= lea th . ab @
‘OF fy) i om | rr
vw 7 ‘Me i
’
>
and = . 3
Lae ~ a t u
Con .
> ;
5 j hl at
a * c * i r ‘
~
in
: in
j + f te 4 y) :
4 i
a e ; ) ‘
f ‘ \ ;
i
= . ‘ = ‘
’ > A
‘
‘ i
7 . % :
‘ I. ;
ae
—s
. ‘
~ fi 4
4 t
; i ,
'
> ‘ »
U ‘
¥
Do ni
La F \ ai
a
1 \ —
q : een ‘
7 iG
3 #
‘
1
i ‘4
-
% ‘
r : :
at
f ' ‘
t
7
‘
.
7
+
)
”
, i
cy!
ye
re
No. 4.—Reports on the Results of Dredging, wnder the Supervision
of ALEXANDER AGASSIZ, in the Caribbean Sea, 1878-79, by the
United States Coast Survey Steamer “ Blake,” COMMANDER J. R.
BARTLETT, U.S. N., Commanding.
(Published by permission of CARLILE P. PATTERSON, Supt. U. S. Coast and Geodetic
Survey.)
VI.
Report on the Corals and Antipatharia, by L. F. Pourtaks.
CORALS.
ALTHOUGH very rich in the number of specimens, the collections made
by Mr. Agassiz in the dredging season of 1878-79 have added but few
new species. Considering the extent of the ground covered (see Bull.
Mus. Comp. Zodl., Vol. VI. No. 1), we may assume that but little will
be added hereafter to our knowledge of the association of corals forming
the West Indian deep-sea fauna. No other region of the ocean-bottom
has yielded so abundant a harvest, and we have therefore no sufficiently
complete data for comparisons with regard to geographical distribution.
But for the bathymetrical distribution, and its bearing on the deter-
mination of the probable depth in which strata of former ages, contain-
ing corals, were deposited, the material brought together in the series
of papers of which this forms the last * will no doubt prove of some
importance.
The following table is a recapitulation of all the species described,
* Deep-Sea Corals, by L. F. de Pourtalés, Illust. Cat. Mus. Comp. Zodl., No. IV.
Zodlog. Results of the Hassler Exped., by A. Agassiz and L. F. de Pourtalés, Ibid.,
No. VIII. Part 1. Report on the Dredging Oper. of the U. 8. C.S. St. ‘‘ Blake,” by
A. Agassiz, L. F. de Pourtalés, and T. Lyman, Bull. Mus. Comp. Zodl., Vol. V.
No. 9. : .
Compare also, for deep-sea corals of the West Indies, G. Lindstrom, Contributions
to the Actinology of the Atlantic Ocean, Kongl. Svensk. Vetensk. Handl., B. XIV.
No. 6; and H. N. Moseley, Preliminary Report on the True Corals dredged by
H. M.S. “ Challenger,” &e., Proc. R. S., No. 170, 1875. Of Mr. Moseley’s final
report I have seen, at the time of writing this, only advance copies of the plates, for
which, and for valuable communications, I am indebted to the author.
VOL. VI. — NO. 4 8
96 BULLETIN OF THE
with their range in depth, and comparisons with other seas, and
European and West Indian fossil faunze : —
aaa aay SA8
Es eSed | 6a.2
soo # Range in | S$.2 S48 Bey
eg Depth. 0 om SES | aaa
Se 4 | BESS | oeaZ
Pons | ae,5> | 8,85
no a) sfonde ae ae
Fathoms.
Caryophyllia berteriana . 56-442 1
antillarum . 82-994
af cornuformis 209-450 iL : x
: communis . 127-892 iis Biuleeerc tae
or maculata 30-88
a polygona 860
Stenocyathus ver miformis 191-460
Thecocyathus cylindraceus . 84-315
che levigatus 100-315
co recurvatus 175
Trochocyathus Rawsonii 82-805
is coronatus 333-861
Deltocyathus italicus 60-888 Ls 1
Stephanocyathus elegans 209-288 -
¢ variabilis . 476 ih $e 1
Leptocyathus Stimpsonii 60-450 1
Paracyathus DeFilippii . 36-805 ae ae
laxus 92-164
hy OSes ve 100
Turbinolia corbicula 100-220
Stephanotrochus diadema 734-1200
Schizocyathus fissilis . 56-450 1
Ceratotrochus typus . 250-400 his 1 1
Flabellum Moseleyi . . 118-476 1
ob angulare . é 888
Desmophyllum erista-galli . 309-805 1 *x
Cailleti 73-1131
" Riisei 88-120
“ solidum . 315 - x
Rhizotrochus fragilis . 84-119
se tulips. 2 84-175
Lophohelia prolifera 195-874 1 1
exigua 36-287
Amphihelia oculata 158-892 1 ay
Madracis asperula 36-180
Axohelia mirabilis : 56-287
Lophosmilia rotundifolia 42-163
Dasmosmilia variegata 60-164
ie Lymani. 70-147
Montlivaultia poculum
Antillia explanata 75 Bis 1
Parasmilia fecunda 68-450 by De 1
Asterosmilia prolifera 45-94 ame, 1
Solenosmilia variabilis 120-805 1
Cylicia inflata 100-242
* Duncan has 35 species of simple and probably deep-sea corals from all the West Indian forma-
tions.
x signifies different but closely allied species.
MUSEUM OF COMPARATIVE ZOOLOGY. 97
sae | Sse | 823
eva, esd. ELm
Range in Sat ema aac ;
Species. Depth. > 3m i B a = ; iz S
sPod | Bed | SPE S
aS & $ Seng | aS oe
a 9 on Perce d (ee Bo ee LS
Fathoms.
Colangia simplex’. 4. |. ‘2 3 . ss | 80-100
_Balanophyllia floridana,. . =. ... « | 26-100 |. . -J|. .. x
; of palilerd ~. « « + «=, » | 36-458
Thecopsammia socialis . . . . . . | 195-262]. 1
ca tintinnabulum . . . . | 120-539
Trochopsammia infundibulum. . . . | 291-805
Dendrophyllia Goést ~ .° . . | $250=400
x altertiatay | s shie oes) | 250-189
ms Gyvarmaides 2. sls 270
a Pormmcopiae =! 5h TOROS Ten Oy ao, 8s x
Stereopsammia rostrata. . . . . « | 164-805
aid profunda .. . . . | 539-805
Mataypeusesymmetrica . . . . . . | 116-805 |. 1
PRRREMINR S Oe0% st aah > yyyer| PLG=189 |... ¢]
MI sw pa mm ny eo, h LLG HEBD
eemerammureta St. et 10088570 (59 1
Duneania barbadensis . . . . . «| 103-191
Haplophyllia paraloxa . . 1.1... 324
Anthemiphyllia patera . . . . . . | 250-400
Total, — 64 species
The .total of sixty-four species is nearly as large as the total of the
shoal-water or reef corals of the same region, if we reduce the number
of the latter, as given by Duchassaing and Michelotti, to its proper
proportions by the rejection of merely nominal species.
The proportion of simple forms to compound ones is very large, —
fifty of the former to fourteen of the latter. The compound ones
belong mostly to the families of Oculinidie, Stylophoridee, and Kupsam-
mide, with one species each from the Eusmiline and Astrangiacee.
Comparing this association with the one prevailing in the same seas
in shoal or moderately deep water, we find that there is not a single
Species in common to both, and that they are separated by an almost
barren narrow zone. We find also that there is not a single simple
species in the shoal-water fauna, and that the compound forms belong
to the families of Astreide, Oculinide, Fungidee, and Madreporide, the
former preponderating by far. There are no Eupsammide. The
nearest approaches between the two horizons would be as follows:
Madrepora cervicornis dredged living by myself in Barbados in 17
fathoms, Orbicella cavernosa in 15 fathoms in Florida, and Mycediwm
fragile in 43 fathoms. The latter species comes in contact with the
98 BULLETIN OF THE
following deep-sea forms: Paracyathus DeFilippii, Caryophyllia
maculata, Lophohelia exigua, Madracis asperula, Lophosmilia rotundi-
Folia, Asterosmilia prolifera, Balanophyllia floridana and palifera, of
which the upper limit is between 30 and 40 fathoms.
For other seas the case would be somewhat different. In the Pacific
and Indian Oceans, for instance, simple corals, as Flabellum and some
other Turbinolide, some Balanophylliz, and numerous large Fungie,
occupy the shoal or moderately shoal water region, and the prevailing
families are different also.
Nevertheless, the West Indian bathymetrical distribution seems to
offer a fair criterion for the approximate determination of the depth at
which some of the strata not lower than the cretaceous have been
deposited. In older formations the forms are too different for com-
parison.
We can thus safely say that some of the miocene, pliocene, and
pleistocene strata of Messina, of which the fossils have been so carefully
described by Seguenza, were deposited in a depth averaging 450 fathoms,
and ranging from abont 200 to 700 fathoms. This average is deduced
from the eight principal species. Two species of Eupsammide would
however give considerably less. The species identical, or very nearly
related, used for this result, are given in the table; some of them still
inhabit the Mediterranean, but others have been found living only in
the West Indian deep-sea. Some of the miocene beds of the vicinity of
Turin are also deep-sea deposits.
In the neighborhood of Vienna it is easy to see by means of Reuss’s
excellent monographs that great fluctuations of depth have taken place
between the deposition of the different strata. The tables appended to
Reuss’s Memoir on the Austro-Hungarian Miocene show very well that the
beds called “ Oberer Tegel,” for instance, in which there are Astreeans in
abundance allied with Porites, are shoal-water deposits; and that the
strata called ‘‘ Badener Tegel,” particularly at Ruditz, were formed on
the bottom of deep water, the corals found in them being chiefly
Turbinolidee, Oculinidee, and Eupsammide.
With regard to the West Indian tertiaries, and more particularly the
miocene beds, a careful discrimination of the corals of the different
strata, such as we have in the papers of Reuss and Seguenza, seems to
be still wanting. Reef corals and solitary species are quoted as from
the same localities in Prof. Duncan’s papers, and in a fine collection
from San Domingo, presented to the Museum by the late W. M. Gabb.
In the latter the different matrix in which some of the specimens are —
MUSEUM OF COMPARATIVE ZOOLOGY. 99
imbedded points directly to different beds. Prof. Duncan’s statement,
that on some islands, such as Antigua and Trinidad, only reef species
are found, shows also pretty conclusively that, in other places there
must be deep-sea deposits which were not brought to light here.
It is rather puzzling to find the West Indian miocene solitary species
so different from the living ones. Even when belonging to the same
genera (see table) the species of the miocene are of a very massive type,
very different from the living; such are the Antilliz and Asterosmilia,
with one exception. It is possible that these massive forms, of which
we have no analogous examples at the present time, may have been
living in the shoal-water, protected by reefs in the same way as the
Fungi, or some of the unattached compound corals, as Manicina or
Isophyllia.
The effect of slow changes of level has to be considered also as a
possible cause of mixture of the dead of one level with the living of
another. |
Caryophyllia berteriana Duca.
Caryophyllia formosa Pourt.
The more the number of specimens of these forms accumulate, the greater
the difficulty to separate them. The principal difference consists in the form
- of the septa, very exsert in C. berteriana, very little so in C. formosa, but 1 now
find many intermediate forms. The number of the pali, 12 to 16, cannot well
be retained as of specific value.
Duchassaing has described as new C. sinuosa, corona, and protet, but the
descriptions either apply to young specimens or to mere varieties of the older
described species.
There is in the collection a specimen taken in the act of swallowing a small
fish, which is partly inside the mouth, with the buccal membrane stretched
from both sides over its middle.
Range * from 56 to 442 fathoms, in 19 stations, off Santa Cruz, Montserrat,
Guadeloupe, Dominica, Martinique, St. Vincent, the Grenadines, Grenada,
and Barbados.
Caryophyllia cornuformis Pourt.
Old specimens show considerable anomaly in the arrangement of the pali,
which are wanting sometimes in nearly one half of the calicle, and their place
filled up by enlarged ribbons of the columella.
A case of involuntary parasitism, like the one mentioned in ‘“ Deep-Sea
* The range in depth in this and the following descriptions refers only to this
year’s work.
100 BULLETIN OF THE
Corals,” was found in this collection. The coral fastened among the pebbles
with which a Phorus has ornamented his shell appears to have flourished
remarkably well in that position, as indeed it ought to, having been carried
about in search of food, and prevented from sinking in the mud.
Range from 200 to 400 fathoms, off Havana and Barbados,
Caryophyllia antillarum Povrrt.
Range from 82 to 994 fathoms, in 11 stations, off Nuevitas Cuba, Mont-
serrat, Guadeloupe, Grenadines, Grenada, and Barbados.
Caryophyllia communis Mos., var. costata.
Ceratocyathus zancleus Src.
Plate I. Figs. 12 and 13.
T agree with Dr. Duncan and Mr. Moseley in joining the genus Ceratocyathus*
of Seguenza to Caryophyllia. The numerous species described by that author
pass gradually into each other. At one end of the series we have the forms
with nearly equal septa and costz, like C. communis; at the other those which
have them very unequal, like C. zancleus. All our specimens are extreme
forms, still more marked in the inequality of septa and coste than the last
mentioned.
As Seguenza has a Caryophyllia zanclea as well as a Curaioeae zancleus,
that name could not well be retained without confusion ; Ceratocyathus costatus,
however, is the same. |
A series of fine specimens shows the mode of growth. The young are erect,
with a thin peduncle attached toa small pebble or shell ; as it grows in height,
the support not being sufficient, it falls over on its broadest side, and the ten-
dency to grow upward, and to keep the calicle above the mud, produces the
curved base. The curvature of those corals which have it in the plane of the
smaller diameter is thus easily explained. It is more difficult to understand
the curvature in the plane of the greater axis, which is the rule in some species
of corals.
The largest specimen measures 36 mm. on the greater diameter of the
ealicle, and 31 on the smaller. None of our specimens have more than 16 pali;
the number can rise to 24, according to Seguenza and Moseley.
Some of the young specimens are still straight, and resemble very much
Moseley’s Acanthocyathus spinicarens.
Range from 127 to 892 fathoms, in 13 stations, off Santa Cruz, Saba Bank,
St. Kitts, Guadeloupe, Dominica, Martinique, St. Vincent, the Grenadines,
Grenada, and Barbados.
* See under the head of Asterosmilia, in ‘‘ Deep-Sea Corals,” a rectification of my
remarks on this genus. .
MUSEUM OF COMPARATIVE ZOOLOGY. 101
Caryophyllia maculata Mos.
Bathycyathus maculatus Pourt.
Mr. Moseley has, I think, rightly placed Bathycyathus in the genus
Caryophyllia.
In 88 fathoms, off Montserrat.
Stenocyathus vermiformis Povrt.
Plate I. Figs. 15, 16.
- Icannot find in my specimens the dissepiments mentioned by Mr. Lind-
strém. His figures represent sections near the centre and near the exterior
wall, where there are connecting bands ; but I have always found the central
part of the chambers unobstructed from end to end. In Pl. I. Fig. 15, I have
given a figure of a decalcified specimen, showing the complete cast of the
inside cavity ; the outside is entirely uninterrupted by any dissepiments, and
shows only the regular little knobs formed by the contents of the small
cavities in the wall. In Fig. 16 twoof the segments are separated so as to
show the bands connecting them between the pali and the septa. ,
Range from 191 to 400 fathoms, in two stations, off Havana and Martinique.
Thecocyathus cylindraceus Povurt.
Range from 84 to 250 fathoms, in three stations, off Havana and Barbados.
Trochocyathus Rawsonii Povurrt.
Specimens fixed by a rather large base are the most common form, free
individuals being comparatively rare. When fixed, there is not much difference
from the genus Paracyathus, unless it is the more regular pali.
_ Range from 82 to 221 fathoms, in four stations, off Grenada and Barbados.
Trochocyathus coronatus Pourt.
Odontocyathus coronatus Mos.
Very fine specimens, both living and dead, were obtained, but no young ones.
Range from 333 to 861 fathoms, in four stations, off Virgin Gorda, Dominica,
and Grenada.
Deltocyathus italicus Epw. & H.
Plate I. Figs. 1-8.
I have adopted the name of the original fossil species for the exceedingly
variable living forms, as Prof. Duncan has done before, the differences between
the living and the fossil being less than between the different living varieties.
The living attain a larger size than the fossil forms.
102 BULLETIN OF THE
About two hundred and fifty specimens of the different varieties of this
species were obtained, so that from the various expeditions we must have
about a thousand specimens. Among that number I have not found a single
one attached, or showing marks of adherence.
There are four well-marked forms, more or less connected by intermediate
ones, thongh, on the whole, specimens showing the passage from one form to
another are rare, and one form generally prevails in each particular dredging.
Variety o, Agassiz. Pl. I. Fig. 2.
The typical form on which I based my first description, equicostate, with
more or less conical base, costz rather prominent, sharp, finely serrate and
granulate. (Deep-Sea Corals, Pl. IL Figs. 1, 2, 3. Lindstrém, Contr. to
Actinol. of Atl. Oc., Pl. II. Figs. 15, 16, 17. Moseley,. Madrep.-of the
Challenger Exped., Pl. II. Figs. 2 and 3.) This form approaches nearest
D. rtalicus ; there are specimens in which the spines of the cost are large and
blunt, and resemble the bead-like grains of the fossil species. (PL I. Fig. 3.)
This was considered by Reuss and by myself as the chief specific difference
between the fossil and living forms. The variety australiensis, Duncan, does
not differ particularly from this one; but D. orientalis, Duncan, is different.
The corals referred to this genus by Mr. Tenison-Woods do not appear to me
to belong here, as far as the very rough figures allow me to judge.
Variety B. PI. I. Fig. 4.
Like the preceding in most particulars, but more hemispherical in outline ;
the cost are a little more differentiated, and the primaries have sometimes a
slight enlargement or blunt knob in the middle of their length, showing a
tendency at one period of their growth to form the points characteristic of the
next form, or variety calcar. The pali in this form are not very prominent,
and the junction of the septa of younger with those of older cycles occurs far
down towards the centre of the calicle. Some specimens resemble very much
Trochocyathus obesus, one specimen of which from Tortone, Italy, in the Muse-
um collection, has likewise only one knob or blunt spine on the primary costee.
Variety y, calcar. Pl. I. Fig. 5.
(Deep-Sea Corals, Pl. II. Figs. 4 and 5, and Pl. V. Figs. 9 and 10; and
Hassler Exp., Pl. VI. Fig. 11. Lindstrém, 1. c., Pl. I. Fig. 13, Pl. II. Figs. 14,
18,19.) I give the figure (Pl. I. Fig. 1) of the specimen, which has induced
me to consider this only a variety of the other form. Besides the specimen
with double horns figured in Deep-Sea Corals (Pl. V. Fig. 9), there is another
one in the present set with three or four horns on the primary cost, appar-
ently the result of an injury. Reuss mentions a specimen of D. italicus with
remarkably thickened, and almost lamelliform, primary and secondary septa,
so that it seems that the fossil form had also the tendency to vary in the same
manner. .
MUSEUM OF CQMPARATIVE ZOOLOGY. 103
Variety 6.—PL. I. Figs. 6, 7, 8.
Base nearly flat, with a sinall umbo in the centre, hardly marked in most
specimens, outline of section somewhat re-entering above, so that the diameter
of the calicle is somewhat less than the diameter of the base. Coste equal,
flat, thick, and contiguous, separated only by a linear though rather deep
furrow, finely granulated, and having a faint granular keel. The pali are
thick, and the columella oblong, composed of thick pillars, and well separated
from the pali; the septa are thickened at the outer borders, covered laterally
by short thick spines. All the specimens are uniformly white, without pur-
plish spots. Moseley’s D. magnificus resembles it in outline, but has not the
same costee, septa, and columella. JI have seen no passages between this form
and the others, when adult, but in the young the coste are thin, and not
essentially different from variety a.
Depth seems to have no influence on the prevalence of one or the other
form.
In the polyps the outer sphincter when contracted covers the tentacles
which are drawn back in the notch between the septa and pali. The office of
the pali seems to be partly to support the buccal membrane, partly to protect
the retracted tentacle. They never support extra tentacles in any of the
corals in which I have had the chance to observe the well-preserved polyp.
Range from 73 to 878 fathoms in 39 stations, off Havana, in Old Bahama
Channel, off Santa Cruz, Virgin Gorda, St. Kitts, Montserrat, Guadeloupe,
Dominica, Martinique, St. Lucia, St. Vincent, the Grenadines, Grenada, and
Barbados.
Stephanocyathus elegans Srcuenza.
Three fine specimens of this species were obtained, two living and one dead.
They agree most with Seguenza’s variety subspinosus.
The second lobe of the pali, generic character according to Seguenza, resem-
bles the parts of the columella, but is well separated from it ; it is not constant,
and distinct only in the second or third order. The columella, which is
formed of twelve or more blunt prongs, is in younger specimens more diffuse.
The septa of the fourth cycle unite through their pali with those of the third,
and the latter with the second. The septa of the fifth cycle are small, and
reach only half-way to the centre.
The polyp has stout tentacles; in one specimen those of the three first
eycles were white, the others dark purple, with white tips; in the other they
were all purple, those of the youngest order least so. They are disposed in
several circles, and do not appear to be very retractile. The outer sphincter is
not distinctly marked. The buccal membrane is very thin, and in both speci-
mens many of the pali had pierced it.
Range from 209 to 288 fathoms, in three stations off Barbados,
104 BULLETIN OF THE
Stephanocyathus variabilis Srecurnza.
Plate II. Fig. 2.
Two specimens, one living and one dead, are referred to this species. They
are both larger than those figured by Seguenza, and differ slightly from his
description. There is no plicated rudimentary epitheca, and the costee remain
very flat and indistinct to the edge of the calicle, instead of becoming ata 8
nent and cristiform. Otherwise there are no essential differences.
The polyp seems to have been rather highly colored, dark purplish in
alcohol in all its parts except the larger tentacles, which are whitish. Ten-
tacles stout, forming a double circle at a considerable distance from the
mouth. Buccal disk radially plicated, and very tough. Diameter of largest
specimen, 48 mm. Height, exclusive of primary and secondary septa, 8 mm.
Height of primary septa, 5 mm.
In 476 fathoms, off Martinique.
Leptocyathus Stimpsonii Poort.
Both the long and the short varieties.
Range from 92 to 400 fathoms, in two stations, off Havana and Genial
Stephanotrochus diadema Mose ey.
Plate Il. Fig. 1.
One living and two dead specimens. The tentacles were remarkably full of
nematocysts, and must have been quite long. Those of the three first orders
are not very different from each other in size, and about equidistant from the
centre; those of the fourth and fifth are smaller and farther removed. The
tentacular circle is quite distant from the mouth, having a large bare plicated
buccal disk.
In 734 fathoms off Guadeloupe, and 1,200 fathoms in lat. 19° 7' N.,
and long. 74° 52’ W.
. Schizocyathus fissilis Pourr.
Range from 56 to 170 fathoms, in seven stations, off Martinique, St. Lucia,
Grenada, and Barbadoes.
Paracyathus laxus n. sp.
Plate I. Figs. 9-11.
Corallum turbinate, turgid, short-pedicellate, sometimes becoming free
when attached to a small object, which then becomes covered up by an
epithecal growth. Generally dark-colored. Costze not prominent, finely
granulated, and separated by a fine linear convex ridge. They are covered by
a very thin rudimentary epitheca, through which the granulations can be seen.
MUSEUM OF COMPARATIVE ZOOLOGY. 105
The calicle is circular, with a moderately deep fossa. The septa are somewhat
exsert, thin, rounded, with granules on the sides, arranged in rows parallel to
the edge. Four cycles and part of the fifth in most of the systems, which are
thus stulercbat unequal. Pali prominent and large, rather irregular, sometimes
two or three lobed ; columella much looser than in the other West India
species. The young have a very loose structure, with thin lamellar pali, and
rudimentary columella not yet developed into pillars.
‘ Largest specimens, 30 mm. high ; diameter of calicle, 19 mm.
Range from 88 to 164 fathoms, in four stations, off Montserrat, Martinique,
and Grenada.
Paracyathus DeFilippii Ducu. & Micn.
Very variable species, which may in the end be found identical with the
Mediterranean species, P. striatus and pulchellus. I have had no opportunity
for direct comparison. : '
‘Range from 56 to 458 fathoms, in sixteen stations, off Santa Cruz, St. Kitts,
Montserrat, Dominica, Grenada, Bequia, and Barbados.
Ceratotrochus typus Povrr.
Conotrochus typus SEG.
Ceratotrochus hispidus Pourt.
“A few more specimens obtained make it evident that the two corals above
named are the same. I have before me specimens entirely or partially covered by.
an epitheca, or completely destitute ofit. The last I have called Ceratotrochus
hispidus. The genus Conotrochus of Seguenza, also adopted by Reuss and
Duncan, must necessarily be dropped, since it differs from Ceratotrochus only
by the presence of an epitheca. Ceratotrochus multispinosus has, according to
M.-Edwards and Haime, a partial epitheca; and, looking over a series of speci-
mens from the Italian tertiary, I find that the character is just as variable, the
epitheca being total, partial, or absent.
It is rather unfortunate to have to retain Seguenza’s specific name for a
species not very typical in its characters.
Range from 250 to 400 fathoms, in two stations, off Havana and St. Kitts.
Flabellum Moseleyi Pourr.
Plate II. Figs. 13 and 14.
Corallum with a rather long and slender peduncle, strongly curved in the
plane of the smaller diameter; a scar of attachment at the end. Calicle
widely open, elliptical, diameters as 1 to 1.3. Margin horizontal. Coste of
the first and second order about equal, forming stout more or less knotty
ridges ; the lateral ones not very different from the others, except in the
younger stages, where they are cristiform. The other costz are represented
106 BULLETIN OF THE
by mere shallow furrows. Angle of aperture abont 40°. The whole surface is
marked with chevron-shaped lines of growth; in one specimen the whole
surface is finely granulated, in the others it is smooth and shiny, as usual in
the genus. The septa are in six systems and five complete cycles. They are
marked with fine radiating granulated ridges. The primaries and secondaries
are about equal, and very exsert; all the others remain below the border of the
calicle, which is deeply indented. There is a callous thickening at the base of
the septa, in the bottom of the fossa. The color of the corallum is a dirty
flesh-color, inside and out. The tentacles are equal in number to the septa; I
_ do not find the small supernumerary ones noticed by Moseley in Fl. alabastrumi
There appears to be no outer sphincter to cover them.
The diameters of the largest specimen are 5 and 4 cm.
It is somewhat related to Moseley’s Fl. alabastrum, but differs from it by its
elliptical outline, long and curved peduncle, and horizontal margin.
Five fine living specimens were obtained.
Range from 118 to 476 fathoms, in six stations, off Dominica, Martinique,
Grenada, and Barbados. 1
Desmophyllum Riisei Ducn. & Mics.
Thalamophyllia Riisei Ducu.
Plate I. Fig. 14.
This is a true Desmophyllum, differing from the typical ones in growing
always in clusters from an incrusting base. It is hardly necessary to form a
new genus for it on that account. I can find no dissepiments, as stated by
Duchassaing.
The corallites are much longer and narrower than in the figure of Du-
chassaing and Michelotti. They are generally 2 or 3 cm. high, with a diameter
of only 5 to 7 mm.
Range from 88 to 120 fathoms, in five stations, off Montserrat, Deiminiios
ae Martinique.
Desmopbhyllum crista-galli Epw. & H.
In 399 and 442 fathoms, off Martinique and Barbados.
Desmophyllum Cailleti Ducu. & Micu.
é
Range from 73 to 1,131 fathoms, in eighteen stations, off Havana, Nuevitas
Montserrat, Guadeloupe, Dominica, St. Lucia, St. Vincent, and Barbados.
Rhizotrochus tulipa Poort.
Range from 84 to 106 fathoms, in three stations, off Barbados.
MUSEUM OF COMPARATIVE ZOOLOGY. 107
Lophohelia prolifera Epw. & H.
A variety with strongly marked primary and secondary costz. ;
In 291 fathoms off Grenada, and in 874 fathoms in lat. 17° 47’ N., and
long. 67° 3’ W.
Amphihelia oculata Epw. & H.
"Numerous specimens, showing much variation, The most common form
agrees exactly with Prof. Duncan’s Figs. 1, 2, and 3 of Pl. XLV. of the
“ Porcupine ” Madreporaria, and is similarly deformed by a parasitic annelid ;
this has apparently the tendency to smooth out the striz. Another variety,
free of parasites, grows into long branches, with alternate calicles, forming
regular zigzags. Often each calicle gives out two opposite ones, one of them
forming the main branch, the other beginning a side branch on the same
pattern. Prof. Duncan’s Fig. 1, Pl. XLVI., shows this mode of growth, but
not with the regularity of some of our specimens. It has also been represented
by Seguenza and by Moseley.. Old branches of this form become much thick-
ened and compressed. Both forms are the same, since they are found in the
same specimen. The strie vary much, and I doubt if they present a sufficient
character to separate A. oculata and ramea. Amphihelia sculpta, Seg., to
which I referred specimens dredged last year, is the same.
Range from 164 to 892 fathoms, in seven stations, off Guadeloupe, Dominica,
Martinique, Grenadines, and Grenada.
Axohelia mirabilis Ducn. & Micu.
Very common, and rather variable. None were found agreeing with
Axohelia Schramm ; but those I had identified as A. myriaster and A. dumetosa
I have now good reason to believe are only differences of age. Old specimens
are generally coarsely striated, somewhat like the figure of A. myriaster given
by M.-Edwards and Haime ; while younger branches are mostly granulated.
As Axohelia myriaster is an East Indian species, I shall use provisionally the
name first used by Duchassaing and Michelotti for the West Indian species ;
but having seen no specimen of the former, I cannot tell in what they
differ.
Among the varieties there is one with slender branches and calicles, raised
on conical projections, as in Oculina varicosa. Specimens obtained from the
telegraph cable off Santiago de Cuba, in 90 fathoms, by Captain Cole of
the Telegraph steamer “ Investigator,” are stunted, sharply striated, the strize
almost ribbon-shaped. The calicles are sunken, often deformed, and some-
times surrounded by shallow open cells, twice as numerous as the septa,
producing a resemblance to some of the double-walled palozoic corals.
Many specimens are deformed by barnacles occupying the end of the
branches, which soon become entirely covered by the coral, with the exception
of a small opening.
108 BULLETIN OF THE .
Range from 56 to 262 fathoms, in twenty-seven stations, off Santa Cruz, Saba
Bank, Montserrat, Guadeloupe, Dominica, Martinique, St. Vincent, Grena-
dines, Grenada, and Barbados.
Madracis asperula Epw. & H.
Range from 60 to 248 fathoms, in six stations, off Santa Cruz, St. Kitts,
St. Vincent, and Grenada.
Solenosmilia variabilis Dunc.
None of our specimens show the blue coloration noticed by Prof. Duncan in
northern specimens.
Range from 120 to 452 fathoms, in six stations, in Old Bahama Channel, off
Montserrat, Guadeloupe, St. Lucia, Grenadines, and Barbados.
Lophosmiilia rotundifolia Epw. & H. .
There is a fine series of specimens of all ages, which positively contradict
Duchassaing’s opinion that the original specimen of M.-Edwards and Haime
was the young of a compound coral, which he has unnecessarily re-named
Oxysmilia rotundifolia. Occasionally two or three individuals grow in a
group, but are not to be called compound for that reason. The lamellar three-
lobed columella is rarely seen as regular as in M.-Edwards and Haime’s
| figure ; it usually thickens in the old, and often becomes irregular. The foot
thickens very much by additions of exothecal cellular roots arranged in con-
centric circles, as in Thecocyathus. The dissepiments are few, but rather thick.
Lophosmilia urena Duch. is probably the same.
Range from 42 to 163 fathoms, in eight stations, off Santa Cruz, Montserrat,
Dominica, Grenadines, and Barbadoes.
DASMOSMILIA Povrt. nov. gen.
Corallum turbinate, with very thin wall, false palli and columella formed by
lobes of the septa ; rudimentary endotheca.
This genus is proposed to receive the two species heretofore named by me
Parasmilia Lymani and Parasmilia variegata, which evidently differ very much
from the typical Parasmilia. The figure of one of the septa of P. Lyman in
my “ Deep-Sea Corals,” Pl. VI. Fig. 10, represents well the principal generic
character.
MUSEUM OF COMPARATIVE ZOOLOGY. 109
Dasmosmilia variegata Pourt.
Parasmilia variegata Pourt.
Bathycyathus elegans STUDER.
Plate II. Figs. 11 and 12.
The wall measures only 0.003 in thickness in a full-grown specimen; few
specimens are therefore obtained entire, and fewer yet are free from deformity
from former breakages. Most fragments seem capable of forming new indi-
viduals by completing lost parts ; sometimes two individuals rise from the septa
of one fragment ; in that case one of them is most probably a true bud.
In 164 fathoms, off Grenada.
Parasmilia fecunda Linpsrr. (Pourt. sp.)
Celosmilia fecunda Pourt.
Cenosmilia arbuscula Pourt.
Blastosmilia Powrtalesi Dunc.
Anomocora fecunda STUDER.
From the examination of a large number of specimens it appears conclusively
that Celosmilia fecunda and Cenosmilia arbuscula are but accidental variations
of the same species. The arbuscula form is the normal one, represented by
shorter and more massive corallites, with well-developed columella; the
fecunda form has grown under circumstances which forced it to elongate
beyond measure, and at the same time to form all its parts, such as the wall,
the septa, and the columella, thinner and more scanty. The extreme forms
are easily distinguished as very different, but there are numberless inter-
mediate ones, often parts of the same stock.
With regard to the apparent budding, numerous alcoholic specimens show
that Lindstrom’s remark, that the young do not arise through gemmation, is
perfectly correct. There is not a single case where the young grows from a
living specimen ; the supposed parent has in every instance the appearance of
having been dead for some time. It is, however, singular, that in many
instances the young are grouped with a certain regularity around, and ata
little distance from, an older calicle. If, then, the propagation is by eggs, there
reinains very little reason for separating this form from Parasmilia proper.
Range from 73 to 450 fathoms, in nineteen stations, off Santa Cruz, Mont-
serrat, Guadeloupe, Dominica, Martinique, St. Vincent, Grenadines, Grenada,
and Barbados.
Asterosmilia prolifera Povcrt.
Ceratocyathus prolifer Pourt.
Paracyathus arcwatus LINDSTR.
Plate II. Figs. 9 and 10.
A careful revision shows that I committed a double error in referring the
specimens in question to the genus Ceratocyathus, and in placing the latter
110 BULLETIN OF THE
among the Trochosmiliacee. The specimens of Ceratocyathus ornatus used in
comparison are true Caryophyllie, while my Ceratocyathus prolifer is a true
Asterosmilia, closely related to Asterosmilia anomala Duncan, from the San
Domingo miocene. It is one of the very few connecting links between the
West Indian tertiary coral fauna and the recent one, while there are so many
between the European tertiary and the present West Indian deep-sea fauna.
A specimen with calicular gemmation has three young ones of different ages
growing out of its calicle, one of them exceeding the parent considerably in
diameter. The latter was still living in the very small part of its calicle left
free, and had formed new septa against the outer wall of some of the younger
ones. The polyp has a well-developed outer sphincter, which contracts suffi-
ciently to cover entirely the tentacles, and close about two thirds of the calicle.
I may as well remark here that Prof. Duncan’s supposition, that the office of
the pali is to support an extra circle of tentacles, is not borne out in this
species, nor in any other paliferous coral of which I have had the opportunity
of examining the polyp. The pali generally show themselves through the
membrane of the buccal disk, which they appear to support.
Range from 76 to 94 fathoms, in three stations, off Grenada and Barbados.
Balanophyllia palifera Poort.
A vertical section shows that the pali are true pali, separated from the septa
by a row of perforations. Large specimens have a few septa of the fifth order.
Range from 82 to 164 fathoms, off Guadeloupe, Grenada, and Barbadoes.
Trochopsammia infundibulum Pouvrt.
A specimen brought up living has the polyp uniformly dark brown, with
thick tentacles, slightly different in size, according to their order, and nearly
in one circle. There appears to be no muscular circle outside of the tentacles.
Range from 291 fathoms, off Grenada, to 424 fathoms, off St. Vincent.
Stereopsammia? rostrata Pourrt.
Amphihelia rostrata Pourt.
This rather abundant coral shows in its younger branches decided Eupsam-
mian characters, the cceenenchyma being perforated in the furrows even at a‘
distance from the calicles; the secondaries are shorter than the tertiaries,
which meet in front of them. In old specimens this character becomes less
distinct, and the perforations are obliterated by an epithecal growth, which is
deposited chiefly on the back part of the branches to a thickness of as much as
two centimeters. The striz are never obliterated by it, but the fine spines
disappear gradually, and old calicles and foreign bodies become quite covered
by it. The projection from the side of the calicle, on account of which the
specific name was given, is very variable, even in the same stock, some calicles
MUSEUM OF COMPARATIVE ZOOLOGY. 111
showing but a slight thickening of one of the septa, while in others as many as
five septa are swelled out, forming a protuberance equal to the diameter of the
calicle.
As the columella is absent or nf ction rudimentary, this coral is placed
provisorily in the genus Stereopsammia, though it differs setabisiel from
the typical species.
Dendrophyllia profunda Pourt. ought to be placed in the same genus.
‘Stereopsammia rostrata is one of the largest West-Indian deep-sea corals;
some of the stocks when entire must have been an inch thick and a foot high.
Range from 164 to 580 fathoms, in three stations, off Santa Cruz, St. Lucia,
and Grenada.
Dendrophyllia Goesi Linpstr.
Like Mr. Lindstrém’s specimens, ours are simple, like Balanophyllia; one of
them shows two buds on its sides. As Lindstrém remarks, it is difficult to
draw the line between Balanophyllia and Dendrophyllia. In the case of
Dendrophyllia cornucopia, for instance, we have in the collection large specimens
without any tendency to bud, which if known alone would certainly be
classed with Balanophyllia.
From 250 to 400 fathoms, off Havana.
Dendrophyllia alternata Pourt. n. sp.
Plate II. Figs. 3 and 4.
Corallum branching more or less in a plane; calicles on the sides, alternate.
Coenenchyma striated, finely and sharply granulated, feeling rough to the
touch. Calicles prominent, and somewhat expanded at the border. Coste
very rough, spines perforated, but not very distinct near the calicle, at a little
distance from which they merge into the striz of the stem. Septa thickened
and rough on the edge of the calicle, coarsely granulated on the sides, often
bent and warped. Four cycles, six unequal systems, the fourth cycle being
unequally developed. The primaries are slightly thicker, and more exsert
than the others. Fossa rather deep ; columella small, but very compact, and
projecting from bottom of fossa, formed of four or five combined parts.
The largest branch is 10 cm. high, 12 mm. in diameter at thickest part; it
seems to have been part of a still larger branch. Calicles 5 mm. in diameter.
This species is allied to D. ramea, but is smaller, and has no terminal
calicles different from the lateral ones.
Range from 150 to 189 fathoms, in three stations, off Guadeloupe, Martinique,
and St. Lucia.
Dendrophyllia cornucopia Pourt.
Range from 73 to 400 fathoms, in five stations, off Havana, Grenada, and
Barbados.
VOL. ‘VI. — NO: 4 9
112 BULLETIN OF THE
Bathyactis symmetrica Mos.
Fungia symmetrica Pourr.
The tentacles are rather small, and are arranged, as in the true Fungie, at
variable distances from the ae according to the order of the septa, but as
in the latter are very symmetrical ; the tentacles are also at regular distances,
according to the cycle.
Range from 116 to 400 fathoms, in thirteen stations, off Havana, Santa Cruz,
Montserrat, Guadeloupe, Martinique, St. Lucia, Grenadines, Grenada, and
Barbados.
Guynia annulata Dunc.
Range from 150 to 357 fathoms, in three stations, off Saba Bank, Montserrat,
and Martinique.
Dunecania barbadensis Pourt.
I group this and the following species together provisionally, but not under
the name of Rugosa, a group which requires revision, and among the characters
of which a tetrameral arrangement of the septa cannot be maintaincd. It is
rather singular that no other specimen of Haplophyllia has been obtained in
all the dredgings taken in West-Indian waters. It is much to be regretted, as
the typical specimen was somewhat deformed.
Range from 103 fathoms, off Barbados, to 191 fathoms, off Martinique.
Anthemiphyllia patera Pourt.
Plate II. Figs. 5 and 6.
The description in my former paper was based ona single specimen. A
number of fine ones obtained this year in the same locality renders it Ree,
to modify it in several points.
The outer surface is covered with a smooth porcellaneous epitheca, without
distinct border, concealing the coste nearly up to the border of the calicle,
where they become somewhat prominent, and beset with short spines. There
is a coarse spongy columella, with flat fasciculate or oftener foliaceous surface.
The interseptal chambers are open down to the bottom, but constricted very
much at intervals by a series of stout half floors or shelves projecting from the
columella outward. The wall is thick. The transversely flattened spines of
the septa are similar to those of Diaseris crispa; similar ones are seen also in
well-preserved specimens of Montlivaultia bormadensis.
I am still in doubt about its affinities ; in general appearance it resembles an
Antillia, but the absence of a complete endotheca is against placing it in that
proximity. It may possibly be related to Discotrochus.
From 250 to 400 fathoms, off Havana.
MUSEUM OF COMPARATIVE ZOOLOGY. rls
ANTIPATHARIA.
In determining the Antipatharia of this collection, an attempt was
made to use the differences in the shape of the polyps, and in the dis-
position and form of the spines, to draw characters for a much-needed
revision of their classification. It is generally conceded that the
division into genera, based mainly on the mode of branching, as estab-
lished by Milne-Edwards and Haime, is not satisfactory. I have used in
former papers the name Antipathes as sole generic designation, and shall
continue to do so for the present, until more material is accumulated.
In Plate III. will be found figures, drawn with the camera, of the
spines of the West Indian species, and of a few others for comparison.
It will be seen that there are at least two different types, — the tri-
angular compressed, and the more cylindrical. The latter are generally
more densely set, even assuming sometimes a brush-like . appearance,
as in Antipathes humilis. (Plate III. Figs. 18 and 19.) They are also
unequal on the two sides of the pinnules, being longer on the side
occupied by the polyps, with a few very much longer ones around the
latter. The triangular spines are disposed regularly in a quincuncial
order around the pinnules, and in a cleaned specimen nothing indicates
the place formerly occupied by the polyps. The only exception to a
more or less spiral disposition of the spines with regard to the axis I
have found in Antipathes (Cirrhipathes) Desbonni, where the spines are
in regular verticils. (Plate III. Fig. 6.) Duchassaing and Michelotti
have figured the same arrangement in Arachnopathes paniculata
D. & M. (non Esper), which I have not seen. In Plate III. Fig. 24,
the spines of a very large apparently undescribed species from Mau-
ritius are figured, showing frequently a secondary point, somewhat like
shark’s teeth.
With regard to the polyps, the drawings herewith presented have the
disadvantage of having all been made from alcoholic specimens, in
various stages of contraction. Still there are differences from one species
to another which cannot be ascribed to that cause. There appears to be
a connection between the shape of the polyps and the shape and dis-
position of the spines. Those species which have triangular spines have
polyps with longer tentacles than those with cylindrical spines, with a
greater tendency to become regular in shape, though there are some in
which the polyp is very oblong in horizontal outline, as in A. tetrasticha.
114 BULLETIN OF THE
Very long tentacles are found in A. spiralis. In very few instances the
tentacles are found retracted, as figured by Lacaze Duthiers; in most
cases they are simply contracted, and in many species they are probably
not retractile at all.
The following species were collected : —
Antipathes (Cirrhipathes) Desbonni Ducu. & Mica.
Plate III. Fig. 6.
In former papers I had used this name for a Cirrhipathes bent in a spiral,
although the above authors state their species to be straight. In this collection
there is a straight form, besides a large number of spiral ones ; and as they are
specifically quite distinct, I retain the above name for the species more fully
described here.
Antipathes growing in clusters, a dozen or more stems from an expanded
root, each stem undivided, slender, straight or slightly bent, but not spiral,
hollow near the end. Spines small and rather blunt, in regular verticils, of
which there are about thirty to a centimeter, each one composed of about
twenty spines. On the older parts of the stem the verticils lose somewhat of
their regularity, but can always be recognized with a little attention. Ver-
tically the spines are also disposed in straight rows, not winding spirally
around the stem. The tips of the stems are membranous and collapsed when
dry, being thin and hollow, with the spines already quite distinct. Longest
stem, 70 cm.; diameter at base, 1.5 mm.
Only one dry cluster was obtained in station 155, 88 fathoms, off Montserrat.
Antipathes spiralis Pavvas.
Plate III. Figs. 5, 25, and 26.
This is the species I had formerly referred to A. Desbonnt Duch. & Mich.
It may be different from Pallas’s species, but I have now no means of com-
parison. Our specimens are all very slender, wound nearly from the base into
spirals 10 to 20 cm. in diameter. The spirals are either from right to left, or
the reverse, and sometimes change from the one to the other in the same
specimen. The spines are short, triangular, compressed, and never in verticils,
but in quincunx. The longest specimen is 3.20 m. long, 4 to 5 mm, in
diameter at the base.
The polyps are alternately large and small, have very long digitiform ten-
tacles, much longer than have been figured of any Antipathes before. (Plate
IIL. Figs. 25 and 26.) The figure represents them as they are frequently dis-
posed, the larger polyps alone being visible, the smaller ones showing only in
the profile view. At other times the tentacles are very much shortened and
stiffened, and stand out like those of A. arborea figured by Dana.
MUSEUM OF COMPARATIVE ZOOLOGY. 115
The ccenosarc on the back part of the branch shows transverse canals more
transparent than the rest, in the spaces between successive polyps.
This species is very common, having been obtained in twenty-three stations,
in depths ranging from 45 to 878 fathoms, off Havana, Santa Cruz, Montserrat,
Martinique, St. Vincent, the Grenadines, Granada, and Barbados.
Antipathes (Rhipidipathes) tristis Ducu.
Plate III. Fig. 10.
Of this delicate species there are several good specimens, 3 or 4 inches high ;
the branches are very slender; anastomoses among them are not plentiful, they
are more properly adherences. The spines are sharp, triangular. (Plate III.
Fig. 10.) The polyps are small, have short digitiform tentacles, and moder-
ately prominent mouth ; the two lower tentacles are sometimes laid around
the mouth, as figured in A. spiralis.
Range from 45 to 226 fathoms, in eight stations, off Santa Cruz, Montserrat,
Martinique, St. Lucia, and Barbados.
Antipathes thyoides Pourr. n. sp.
Plate III. Figs. 17 and 31.
Densely flabellate, but entirely without adherences of the branchlets, which
ramify from the sides of the branches without showing any regular pinnate
arrangement. The finer branchlets show an apparent succession of swellings,
produced by the larger spines surrounding the polyps. The spines are of the
cylindrical type, unequal, with a few very long ones about the proximal end of
every polyp. (Pl. III. Fig. 17.) The polyps are of the sessile type, with
very short tentacles. (PI. III. Fig. 31.)
The largest specimen spreads 20 cm. in height, and 30 cm. in breadth.
In 124 fathoms, off St. Vincent.
Antipathes picea Poort. n. sp.
Plate III. Figs. 9 and 29.
Branching, flabellate, the branches With four rows of pinnules, two of which
remain generally small and simple, while the two others develop more and
give the pinnate appearance to the branches. These larger branchlets are
again beset with small pinnules on one side. This is precisely the same
arrangement as in A. tanacetwm, from which it differs by the spines, which
are in the latter species about three times as long as broad at the base, while in
A. picea they are about as high as broad. The polyps are small, with a large
spherical buccal knob and flattened tentacles, with slightly incised border ;
when strongly contracted they appear globular. They are thickly beset with
bundles of lasso-cells. On the thicker branches the polyps are rare, and have
116 BULLETIN OF THE
distant and rudimentary: tentacles ; on the main stem very few buccal knobs
are found, and these entirely destitute of tentacles.
Height of specimens 20 to 25 cm. 86 Nab
Station 260, 291 fathoms, off Grenada. Station 286, 7 to 45 fathoms, off
Barbados. )
Antipathes tanacetum Pourt. n. sp.
Plate III. Fig. 13.
The mode of branching and the spines have been described under the pre-
ceding species, and the differences pointed out. This species remains mostly
with a simple stem, rarely branching a few times, and has much the appearance
of a leaf of tansy or yarrow. On the lower part of the stem the spines
become very slender and branching like miniature deer-horns, forming a
velvety covering, which becomes filled with grains of sand, sponge spicules, &c.
The polyps were badly preserved, but evidently very small.
Most specimens have a parasitic worm, resembling very much, and perhaps
identical with, the one which produces the tube in A. colwmnaris; here
however, it remains applied to the stem, partly protected by the branchlets,
but producing no change in their growth.
Range froni 88 to 170 fathoms, in eight stations, off Santa Cruz, Montserrat,
Dominica, Martinique, the Grenadines, and Grenada.
Antipathes filix Pourrt.
Plate Ill. Figs. 15 and 16.
My original description of this species was based on simple and younger
stocks; it, however, branches in a subflabellate manner, spreading 30 to 40.
cm., more in breadth than height, and assuming then a general appearance
with A. myriophylla of the East Indies, with which I have confounded it when
in this state (Bull. Mus. Comp. Zool., Vol. V. No. 9). It differs from it-greatly
in the arrangement of the pinnules and spines. The long spines surrounding
the polyps are beset with little knobs at the end, giving them a rugose appear-
ance. In A. myriophylla (Pl. III. Fig. 23) the spines are all equal.
The polyps are small and inconspicuous, and of the type of those of A.
humilis (Pl. III. Fig. 32).
The differences between this species and A. abietina are not great, the spines
and polyps presenting no particular differences. The latter species may be
distinguished, if it is not considered a mere variety, by its greater stiffness, and
by being regularly pinnate instead of having pinnules in every direction.
Range from 76 to 287 fathoms, in twenty stations, off Montserrat, Martinique,
Dominica, Guadeloupe, St. Vincent, the Grenadines, and Barbados.
MUSEUM OF COMPARATIVE ZOOLOGY. pay
Antipathes eupteridea Lamx.
Plate III. Fig. 11.
The very scanty description of this species, the type of which came from
Martinique, leaves it a little doubtful if our specimen can be referred to it.
Lamouroux compared his specimen to a peacock’s feather. Ours is branching,
resembling very much some of the larger Plumularide, — Cladocarpa paradisea
Allm., for instance. The specimen, the main stem of which was dead at the
top, must have been about 40 to 50 cm. high. The pinnules are 40 mm. long.
The spines are nearly cylindrical, rather dense, subequal, very little longer
about the polyps. The polyps are very small and sessile.
~ Station 203, 96 fathoms, off Martinique.
Antipathes salix Pourt. n. sp.
Plate III. Fig. 8.
Irregularly branching, with long slender pinnules, not disposed in any par-
ticular order, the whole appearing somewhat like a miniature weeping-willow.
The spines are equal, long triangular, somewhat hooked upward, rather close
set. On the larger branches they form longitudinal rows, more or less regular.
The polyps are very small and inconspicuous, of the sessile type.
It resembles somewhat Aruchnopathes paniculata Duch. & Mich. (non
Esper.), but is more flexuous, has no coalescent branches, and the spines are
not in verticils. :
Station 171, 183 fathoms, off Guadeloupe.
Antipathes rigida Pourt. n. sp.
Plate III. Fig. 12.
A small specimen, differing from the preceding only in being stiffer, with
thicker pinnules and occasional coalescences of branches. The spines are very
much like those of the preceding species, only not quite as densely set. The
polyps are of the same type.
Station 273, 103 fathoms, off Barbados.
Antipathes columnaris Ducu.
Plate III. Fig. 3.
The spines are very small, triangular, and blunt, somewhat longer at the tip
of the pinnules. The polyps are rather abundant on the network forming the
tube for the parasitic worm. ,
Range from 73 to 861 fathoms, in sixteen stations, off Guadeloupe, Marti-
nique, Dominica, Virgin Gorda, St. Lucia, St. Vincent, the Grenadines, and
Barbados,
118 BULLETIN OF THE
Antipathes humilis Pourt.
Plate III. Figs. 18, 19, and 32.
The most densely spinous species which has come under my observation.
Range from 76 to 262 fathoms, in four stations, off Montserrat, Grenada, St.
Vincent, and Barbados.
| There are several species described by Duchassaing and Michelotti,
and by the former alone in his Revue des Zoophytes et Spongiarres des
Antilles, Paris, 1870, which are too briefly characterized for identifica-
tion. The large species which I had formerly referred to A. dissecta
D. & M. is A. glaberrima Esper.
Fig.
calcar.
Fig.
Fig.
Fig.
Fig.
os
16.
MUSEUM OF COMPARATIVE ZOOLOGY. 119
EXPLANATION OF THE PLATES.
PLATE I.
Deltocyathus italicus, showing passage from variety Agassizii to variety
Deltocyathus italicus, variety a, Agassizii, section magnified.
Coste of the same, magnified.
Deltocyathus italicus, variety 8, section magnified.
“< ‘s “¢ y, calcar, section magnified.
“ rT ‘* 6, section magnified.
my rT: ‘¢ 6, costz magnified.
‘ “ *« 6, calicle magnified.
Paracyathus laxus, profile, nat. size.
Te “s ealicle, ee
6 ‘¢ section, Be
Caryophyllia communis, variety costata, nat. size.
“ “$ ~ ‘‘ ealicle, nat. size.
Desmophyllum Riisez, nat. size.
Stenocyathus vermiformis, portion decalcified, magnified.
‘a re or two segments separated, to
show interrupted connections at the centre.
bj
kd
OQ
Ga" de" da’ da’ da" da’ da" da" da’ da" da" da" da’ gi
~
rae ee ee)
SS ae
fal ped
at SS)
rer
BEV CONROE
PLATE II.
Stephanotrochus diadema, specimen with the polyp aa in alcohol.
Stephanocyathus variabilis, * *
Dendrophyllia alternata, nat. size.
i es calicle magnified.
Anthemiphyllia patera, section 3
66 66 septa 66
Paracyathus flos, profile, nat. size.
= ‘* calicle, big
Asterosmilia prolifera, calicle, nat. size.
6é 6é profile, sé
Dasmosmilia variegata, profile, nat. size.
= a calicle, a
Flabellum Moseleyi, profile, nat. size,
se - calicle, .
120
Pig: “1s
Fig. 2.
Fig. °S.
Fig. 4.
Fig. 5.
Fig. 6.
Big: i,
Fig. <3;
Fig. 9.
Fig. 10.
Fig: ‘11.
Fig. 12.
Fig. 13.
Fig. 14.
Fig. 15.
Fig. 16.
Fig. 17.
Fig. 18.
Fig. 49,
Fig. 20.
Fig. 21
Fig. 22.
Fig. 23.
Fig. 24.
Fig..'25.
Fig. 26.
1
*
BULLETIN OF THE MUSEUM OF COMPARATIVE. ZOOLOGY.
ig. Zi
. 28.
ig. 29.
. 80.
ods
. 32.
PLATE III.
Pinnule of Antipathes tetrasticha, magnified 10 diameters.
Je “ glaberrima, be
ey ss columnaris, cig a
6é 6é lenta, 6é 6é
Stem of Sf spiralis, “ | Sot
9 “ Desbonni, oe of
Membranous tip of Antipathes Desbonni, <* oa
Pinnule of Antipathes salix, e 5
be ee picea, 6é ce
‘“c 66 tristis, GG ‘6
“ i eupteridea, si ms
6c 66 rigida, 66 7
os oF tanacetum, ka ei
“ ee abietina, € PE
rT rT filix, 66 cc
Spine of af Jilix, magnified 230 diameters.
Pinnule of ‘“ thyoides, magnified 10 diameters.
oH = hunvilis, a o upper view,
‘6 66 ‘ 66 66 “6 lower view.
a oe Fernandezit, zis pe
6é 66 arborea, 6é 66
sf e reticulata, .
id oe myriophylla, ie zi
Pinnules of Antipathes, sp. from Mauritius, magnified 10 diameters.
Side view of contracted polyps of Antipathes spiralis, showing smaller
polyps concealed under the arms of the larger, magnified 10 diameters.
Upper view of contracted polyps of Antipathes spiralis, the small polyps
showing but one or two tentacles ; the tentacles of the large one in the middle are
now contracted.
Polyps of Antipathes lenta, magnified 10 diameters.
ێ oe
6eé ce
66 66
6é ce
6é ce
glaberrima, ‘* %
pi Col, 66 73 >
tetrasticha, ‘* “
thyoides, ot mH
humilis, a ig
CAMBRIDGE, February 6, 1880.
A.Meisel, Lith
:
f
i Lay
: J 1 >» é
7 fem
a a
lo we
" ”
f E
: : ‘
one
i
; = 1
.
: }
on fy ha \
y ey AS
if ral
ra eae ‘
i i ek Tom i Or
ay
f dj ale ah hea \y
7 \ ar | ae
Fi y Nee ha
i
rs
‘ : ,
i
a , 1
; q ' \e “
1 9 hike {
ai os
2M wo rime
:
?
P '
bs
ee
f
{
\
£
ii,
i ’
i
; }
& #
,
Sa
: By iy
{ M
‘. }
\
1
.
P ne
*
‘ ‘
j
> i!
P
«q
* £0)
4
{
J
/
i oa
wy
ia, |
Aan |
l iw
Raa
A. Meisel, Lith
i
‘
,
i
\
‘
,
"
' Feil
f i
.
‘
tne,
=
i
} % =
v
i
! i
" 4
2
j
’
t
{
/
«
©
i
4
=
{
x
j
aa
Ll
P
~ ~~» Pe A
a aA Ss aA OR
So o0U a 6
ne per’ od re ww ~~
7 wi wey wee
ITS D peice
‘ lx!
— soSe Se Se OS
= a a >
Ps a ~ _ =<
2 2 2. SS Na been 8
: = = => 1
a ed oe PV PATE Pir yvyyy ee
A ee a ap & N
Reo a a ey
ey 02 py Dapp
ey
= = = << en
Ae iat Oy ey alr he ay SP”
OL
dado day
1 ——_ 4 F 2 a Ss — La
VOM TV YWIS TH 7 FF
N
roel
A A DS 4
ee a DAXD AAA
cl
bass |
2 ‘inten
Se eS as bee” Pe oat eae)
- =
5 2
Ta a gem aaa cel ey en nt nt a
a
A Meisel, ith
A i
igs’
re j
J " ’
: ;
No. 5.—The Ethmoid Bone in the Bats. By Harrison
ALLEN, M. D.
A coMPARISON of the ethmoid bones of the bats, upon which I have
been of late engaged, has resulted in defining some interesting points
in the anatomy of the organ of smelling in these animals. Awaiting
opportunity for framing more elaborate descriptions, I propose formulat-
ing an account of the peculiar appearances of the ethmoid in the various
families. I may here state, that, in every example I have examined, the
detail in the arrangement of the scrolls of the ethmoid bone has yielded
characters by which the genera and even the species can be readily
determined.
The genera examined are the following: Pteropus, Hpomophorus,
Rhinolophus, Phyllorhina, Megaderma, Nycteris, Antrozous, Plecotus,
Corimorhinus, Vesperugo, Vesperus, Scotophilus, Atalapha, Vespertilio,
Natalus, Miniopterus, Emballonura, Taphozous, Noctilio, Molossus,
Nyctinomus, Chilonycteris, Mormoops, Macrotus, Vampyrus, Schizostoma,
Phyllostoma, Carollia, Glossophaga, Artibeus, Vampyrops, Stenoderma,
Chiroderma, Sturnira, Brachyphylla, Centurio, and Desmodus.
The identifications of Dobson (Catalogue of the Chiroptera Br. Mus.,
1878) have been accepted in framing the above list.
In all the genera examined, the ethmoid bone is composed of a ver-
tical lamella projected from the cribriform plate, to which in most in-
stances there is appended an outer (lateral) horizontal scroll.
(1.) In its simplest form, the vertical plate bears upon its median
surface one or more rudimental scrolls. Examples of this variety are
seen in the Nycteride. In Nycteris, Rhinolophus, Phyllorhina, and
Megaderma spasma, the rudimental scrolls are horizontal ; but in Mega-
derma frons they are vertical. The outer (lateral) scroll, which is
present in NVycteris and Phyllorhina, tends to be directed inward.
(2.) In the next degree of complexity met with, the vertical lamella
resembles the foregoing, but possesses a small lateral scroll, which arises
independently from the cribriform plate. The vertical plate retains
upon its median aspect two vertical rudimental scrolls. Example, the
genus Hmballonura.
VOL. VI. — NO. 6
122 BULLETIN OF THE MUSEUM OF COMPARATIVE ZOOLOGY.
(3.) In the third degree of complexity the vertical plate is revolute
anteriorly, and (as seen from above) is sub-triangular or cylindroid in
form. It retains upon its median surface two supplemental horizontal
or oblique scrolls. The outer (lateral) scroll is present.
The vertical plate may project well in advance of all the other parts,
or may be but slightly longer than they. No union exists between the
outer (lateral) scroll and the vertical plate of the frontal bone in the
orbit. Examples, Vespertilionide, the genus Molossus, its congeners, and
Noctilio. Natalus is remarkable for lacking the outer (lateral) scroll.
In Molossus, Nyctinomus, and Noctilio the vertical plate projects
scarcely at all in advance of the median supplemental scrolls, and never
appears on the median surface below the level of the scrolls. In Ves-
pertilionide it forms a conspicuous tapering process. It is seen below
the plane of the supplemental scrolls in Atalapha noveboracensis and
Vesperus noctivagans.
(4.) The vertical plate is short and ends abruptly anteriorly. It is
visible beneath the supplemental scrolls on the median surface. The
outer (lateral) scroll is as long as the vertical, and is united to the ver-
tical orbital plate of the frontal bone. Example, the. genus Zaphozous.
(5.) The vertical plate is produced in advance of the position of the
supplemental scrolls, as in the last-named group, but is compressed from
side to side as seen from above, and is not revolute. It bears upon
its median aspect posteriorly a lobule. The supplementary scrolls in
general appearance are much as in the Vespertilionide. The lateral
scroll is cylindroid. Examples, the Phyllostomide.
In Desmodus, the lobule upon the anterior portion of the vertical
plate is relatively large.
(6.) The vertical plate is projected far in advance of the supplemen-
tal scrolls, which are horizontal in position and four in number. The
lateral scroll is more or less adherent to the vertical plate, or by its
outer border to the frontal bone. Examples, the Pteropide.
The Pteropide, Nycteride, and some Phyllostomide have a horizontal
septum passing transversely from the under free edge of the vertical
plate (as it lies beneath the lowest median supplemental scroll) to the
nasal septum. The olfactory surface in such forms is thus withdrawn
from the respiratory currents, since no direct outlet exists at the pos-
terior nares.
The above descriptions have been drawn, for the most part, from
specimens in the fine collection of the Museum of Comparative Zodlogy,
Cambridge, Mass.
FEBRUARY, 1880.
No. 6.— On certain Species of Chelonioide. By SAMUEL GARMAN.
In this notice three species of Sea Turtles are mentioned, of which
two are supposed to be new.
About three years ago, Richard M. Kemp, of Florida, directed my
attention to a peculiar Turtle, commonly called the ‘ Bastard,” found
in'the Gulf of Mexico, and said to be across between the Green and
Loggerhead, Chelonia mydas and Thalassochelys caowana. At a later
date he secured for the Museum a pair of fine specimens, which furnish
the material for a description given below. In consideration of the
great interest Mr. Kemp takes in matters pertaining to natural history,
it is most appropriate that the species he has been the means of bring-
ing into notice should bear his name.
There is considerable likelihood that the other species, of which de-
scriptions are given, have heretofore been considered as one, Chelonia
virgata. If this has been the case, a very slight comparison of the
characters assigned will convince any one of the necessity of separation.
Of the various names that have been applied by different authors to
C. virgata, none can be said with certainty to belong to the flat, broad
species which has probably been associated with it. Consequently, it is
thought better to apply a name not previously employed in connection
with either of them, thus avoiding confusion, rather than to make use
of a synonyme concerning which there will always exist more or less
doubt.
Thalassochelys Kempii sp. nov.
Body depressed, short, broad, subcircular, with a slight concavity over the
lateral marginal plates of the carapace, and without the prominent rounded
hump on the vertebral series over the pelvis or shoulder girdle, as in T. caou-
ana. Head intermediate in size between that of T. caouana and that of
Chelonia mydas, crown slightly convex. There is a shallow depression from the
eye forward. Looking from above, the outline of the face is much more convex
than in either of the species cited. A low, broad, rounded ridge extends from the
nostrils to the point on the end of the beak. The lateral outline of the jaws
VOL. VI. — NO. 6.
124 BULLETIN OF THE
is very convex forward. Upper jaw without serrations, lower outline forming
a sigmoid curve, convex posteriorly, and concave near the extremity, where it
suddenly descends to the sharp point at the symphysis. The greatest con-
vexity occurs at a point below and in front of the eye. Lower jaw strong,
without serrations, upper edge concave, curving upward in a point on the
symphysis. Frontals, two pairs. Vertical small, narrow, hexangular. Two
supraorbitals on each side. Interparietal large, broad, surrounded by thirteen
plates (9-13). Postorbitals, three, upper small, lower narrow, elongate. Cara-
pace with little or no indication of a hump on the first or ultimate vertebral
plates, outline slightly straightened over the hind legs, indented over neck and
arms, with five shields in each series of costals and the vertebral. Anterior
vertebral shield short and narrow, second to fourth narrow and long, posterior
longer and wider. First pair of costals small. Marginal plates, twenty-seven,
anterior very narrow, becoming wide on the flanks from the fourth. From the
middle of the body back the marginal shields are subequal, excepting the
caudal pair, which are wider, but without being produced beyond the general
outline. Eight or ten of the posterior marginal bones of the skeleton are
joined by suture to the broad costals, making for the hinder half of the cara-
pace nearly solid bone. Paddles medium, each with two nails, anterior long
and narrow, posterior short and broad, margins indented between the digits.
In one specimen the width and length are equal, twenty-six inches; in the
other, the width is twenty-nine inches, while the length is only twenty-eight.
Both are quite aged, as is shown by the ossification of skull and carapace, and
by the worn appearance of jaws and scales.
Distinguished from 7’. caouana by the short, round body, low humps, mar-
ginal plates, narrowness of head across occiput, and swollen jaws; from
T. olivacea by shape of head, swollen jaw, and plates of the carapace. The
compression of the anterior portion of the head of T. olivacea at once separates
the species.
“The Bastard Turtle are common. We know that they come on the beach
to lay in the months of December, January, and February, but cannot tell how
often, or how many eggs they lay at a time. They can be secured quite readily,
but are not sought for. Hawksbill, Loggerhead, and Green Turtle lay in
April, May, and June.” (Kemp.)
Some of the characters by which this turtle is distinguished from caouana
and olivacea are of more than specific importance,— namely, shape of head
and body, and skeletal peculiarities. According them a subgeneric value, the
habitat suggests the name Colpochelys, from xéAmos, a gulf. This will give to
this species the name Colpochelys Kempwt, Kemp’s Gulf Turtle.
Chelonia depressa sp. nov.
Young. — Body a broad oval; head large, rounded posteriorly, occiput
convex, flattened between and compressed in front of the eyes. Jaws not ser-
rate (in very young), upper with a shallow notch in front, lower with a sharp
MUSEUM OF COMPARATIVE ZOOLOGY. 125
curved prominence at the symphysis. Carapace broad, arch comparatively
low, with three low ridges, slightly concave near the margin. Paddles broad,
rounded on the margins.
Adult. — Body broad, depressed, subelliptical, broadest near or behind the
middle, concave near the iateral margins, flattened over the second to the
fourth vertebral plates ; head larger and broader than that of C. mydas or
C. virgata, broad posteriorly, convex on the occiput, flattened between and
compressed in front of the eyes. Upper jaw not serrated, outline nearly
straight, with the notch at the symphysis almost obliterated, vertically grooved
on the inner face. Lower jaw serrated, bearing a curved fang-like prominence
on the symphysis. Carapace broad and spreading posteriorly, arch very low.
Paddles comparatively small, anterior narrow and pointed, posterior short,
truncate, indented between the digits. One pair of elongate frontals. Ver-
tical small, short, broad, pentagonal, acute-angled in front. Supraocular large,
broad. Interparietal broader than long, surrounded by seven plates, vertical,
supraoculars, parietals, and occipitals. Postorbitals four (8-4), lower large.
Plates of carapace not imbricate, smooth in young and adult, costal series four
each, five vertebrals, and twenty-five marginals. Sternal plates thirteen, in
two series of six each, preceded by a small triangular plate at the neck. Lateral
plates of plastron four on each side, preceded by a pair of small, and these
again by several smaller brachials. The specimens described are from the
East Indies and North Australia. Applying the line to the shell the Aus-
tralian specimen measures in length 364 inches, and in width 30 inches ; its
height is 9 inches. A specimen of C. mydas has a length of 393 inches, a width
of 343 inches, and a height of 11 inches. /
C. depressa differs much from the species described by Dumeril and Bibron
as C. virgata. It is less truncated and more deeply indented in front than
either of the other species of the genus. A transverse section across the
middle of the body is not what would be called roof-shaped, but more of the
shape of a bow of considerable curvature, a portion of the middle of which
is straight, and of which the extremities are sharply turned upward. The
sides are not strongly arched, and the cross-section of a large specimen could
not be described as forming an open angle. The broadness of the head, the
marked difference in shape from that of C. mydas, and the concavity near the
lateral margins, could not have escaped the notice of the authors of the
Erpétologie Générale, if there were specimens of this species at hand. Their
description applies either to the species renamed by Dumeril and Bocourt
C. Agassiz, or to one much more closely allied to it than that described
above. If the separation of C. Agassiziz from C. virgata of authors is right,
there exists a third species of Chelonta in the Northwestern Pacific and
the northern part of the Indian Ocean. The specimens from which the de-
scription in the Erp. Gen. was taken were said to be from Teneriffe, Rio
Janeiro, Cape of Good Hope, New York, and the Indian Ocean, which dis-
tribution can leave little doubt that they were of more than one species.
126 BULLETIN OF THE MUSEUM OF COMPARATIVE ZOOLOGY.
Chelonia Agassizii Dumerit & Bocourt, 1870.
? Chelonia virgata ScHWEIGGER, 1814.
Chelonia virgata AGAssiz, 1857.
Carapace subcordiform, considerably arched, narrow posteriorly ; margin
with a shallow indentation over neck and each arm, and a deeper one over
each leg. Head moderate, about the size and shape of that of C. mydas, more
compressed and pointed in front of the eyes than that of C. depressa. Upper
jaw not serrate on the edge, with grooves on the inner face corresponding to
the teeth on the lower, with a slight notch in front. Lower jaw serrated on
the edge, bearing a prominent curved point on the symphysis. Serration of
jaw not apparent in very young specimens. Frontal plates one pair, sometimes
subdivided. Vertical small, narrow. One supraocular on each side. Inter-
parietal moderate, surrounded by seven plates; supraoculars and vertical in
front, and a pair of large plates behind on the occiput. Postoculars four. Cen-
tral plates of carapace thirteen, vertebral series five, anterior and posterior
wider, posterior costals and vertebrals sometimes divided; marginals twenty-
five, posterior sometimes fused. The anterior and posterior plates of back are
rather suddenly bent downward near the margin. The tail of the male is
longer ; it appears that the pointed extremity of the carapace is also more
elongate in this sex.
Specimens described from the eastern portion of the tropical Pacific.
CAMBRIDGE, March, 1880.
No. 7.— Contributions to a Knowledge of the Tubular Jelly-fishes.
By J. WALTER FEWKES.
I. The Development of the Tentacular Knob of Physophora
hydrostatica.
THE anatomy of those animals known to the zodlogist as the Sipho-
nophore, or tubular Jelly-fishes, has been carefully studied, and minutely
described. I present certain points in which my observations or conclu-
sions differ from those of other naturalists. I have also discussed at
length the limits and synonymy of the genus Halistemma, since I think
it embraces animals with generic differences, and I conclude with a brief
mention of North American Siphonophore and Velellidz, adding three
genera to those already described for our coasts. The development of
the structures which have received the name of tentacular knobs has a
certain interest, particularly the different stages in growth of that per-
haps most complicated of all, the knob of Physophora. The development
of these structures long since attracted attention, and Claus * twenty
years ago (1860) published a description, with figures, of the younger
stages of the knob in Physophora hydrostatica. Keferstein and Ehlers,
to whom science owes so many discoveries in regard to these Jelly-fishes,
followed this work with certain corrections and additions of the most
important character. Their investigations were made upon a species of
Physophora called P. Philippi, identical with or only distinguished from
P. hydrostatica by the possession of lateral appendages to the external
walls of the knob. The account which they give in most particulars
applies also to P. hydrostatica, which’ has furnished me the material for
my studies of the developmental history of the tentacular knob in this
genus.
The growth of the knob of Physophora, although quite simple, is more
complicated than that of any other Siphonophore. I have only, how-
ever, considered it necessary to figure a few stages assumed in this
growth, illustrating the peculiar asymmetrical form of the involucrum,
and the embryonic appendages to the sacculus, which are provisional in
* Ueber Physophora hydrostatica nebst Bemerkungen itiber andere Siphonophoren.
VOL. VI.—wNO. 7. 1
128 BULLETIN OF THE
their nature, and give the early condition of the knob a likeness to that
of certain other genera of Physophoridee.
The knob of Physophora hydrostatica originates, like that of other tu-
bular Jelly-fishes, as a simple bud, hardly distinguishable from the earlier
condition of all structures in the Siphonophores. In its place of origin it
resembles the genus Agalma, for it forms on the ciliated base of the feed-
ing polyp, and is in fact a proliferation of the walls cf that part. Whether
all Physophore knobs originate from the same relative position is an
open question. In Rhizophysa filiformis we have several of the polypites
nearest the float with naked tentacles, from which the knobs bud, never
arising from the base of the polypites. Of course these undeveloped
appendages in the singular Rhizophysa may be looked upon as tasters,*
a supposition hardly probable ; or it is also possible that they correspond
with somewhat similar structures between the nectocalyces of Apolemia
uvaria. In the well-known genus last mentioned the polyp-like parts
between the swimming-bells appear to have no filaments like those
found on the tasters of other Siphonophores. The taster-like bodies near
the float of Rhizophysa are undeveloped feeding polyps.
In the very earliest stages the Physophora knob is composed of layers
which are apparently two in number. The differentiation of other
layers takes place later in the course of the development. At first we
find only ectoderm and entoderm in the walls of the knob. This simple
bud elongates into a flask-shaped body, at the base of which the cavity
becomes enlarged, imparting to this region a more or less spherical shape.
(Pl. I. fig. 2.) From the ectodermic wall of the enlargement thus formed
arises the involucrum. An éxamination of this region, even at an early
period (Pl. I. fig. 3), shows that a differentiation has begun, and that the
ectoderm has divided into two layers, one of which appears as a collar
* The word taster, to designate peculiar structures among the Siphonophores, is
perfectly applicable in the case of Physophora. In other genera the designation
‘“‘Saftbehalter” may seem better; but here in Physophora their function seems dif-
ferent from that of the same part in most of these animals. The filamentary append-
age to the taster in Physophora, although very easy to see, has been overlooked by
several naturalists. (See Kolliker, Schwimmpolypen von Messina. Vogt, Siphono-
phores de Nice. Leuckart, Siphonophoren von Nizza, p. 106.) According to Kefer-
stein and Ehlers (/. ¢c., p. 31), these appendages to the taster were discovered by
Philippi, but were omitted in the descriptions by naturalists who followed him until
the investigations of Sars. In his Anatomy of Physophora, Claus (1860) speaks of
them (p. 17), but has no representation of the filament in his figure of the genus.
(Claus, Ueber Physophora hydrostatica nebst Bemerkungen iiber andere Siphonophoren,
Zeitsch. f. Wiss. Zool., Bd. X. p. 1, fig. 1. Philippi, in Miiller’s Arch. f. Anat. u.
Physiol., p. 61, Taf. 5, fig. 4. Sars, in Middelhavet’s Littoral Fauna, p. 4.)
MUSEUM OF COMPARATIVE ZOOLOGY. 129
around the base of the knob. If we watch the growth of this collar,
which is the outer differentiated layer of the ectoderm, it will be found
to gradually grow down around the sacculus until it has almost com-
pletely enclosed it, leaving, however, an opening at the distal pole of the
knob, through which the end of the sacculus, or certain appendages to
the extremity of this organ, project. (PI. I. figs. 4, 5.)
Meanwhile, the sacculus has passed through certain changes, the most
important of which is a coiling up of itself within the envelope of the
involucrum, and the formation at its extremity, where it projects through
the opening of the involucrum, of certain appendages of a provisional
nature. The earliest condition of the sacculus is simply the terminal
transparent part of the flask-shaped body already mentioned. It is
now a complicated organ armed with lasso cells, and with its walls
highly colored. The provisional structures at the distal end of the
sacculus (Pl. I. figs. 4, 5, 6, 8) are mentioned and figured by most of
those who have studied the young knob of Physophora. They have
been seen in both species, but do not appear to exist in the fully de-
veloped form of the knob, either in P. hydrostatica or P. Philippi. The
accompanying growth of another part of the young knob is destined to
change materially the appearance of the whole, as well as the relative
development of the parts. This change takes place contemporaneously
with the enclosure of the sacculus by the involucrum, and the appear-
ance of those provisional terminal filaments which I have already men-
tioned. The alterations of form to which I refer are as follows. The
proximal or basal part of the spherical-shaped expansion of the young
knob enlarges on ong side, and in such a manner that the knob as a
whole assumes an asymmetrical shape. (Pl. I. fig. 4.) This want of
symmetry is brought about by an unequal growth in the two sides of
the basal part of the knob itself. In a still more developed stage of the
Same structure the inequality in growth has gone still further, and the
enlargement lengthens and extends along the side of the sacculus, now
coiled on itself, carrying with it the former place of attachment of the
sacculus, which is to be found at the opposite pole from its former junc-
tion,” (Pl. I. figs. 5, 6.)
Meanwhile the knob is approaching its fully-grown form, and the ter-
minal filaments become absorbed ; the opening at the distal pole of the
involucrum closes or is very much reduced in size, and the enlargement
in the spherical cavity, which earlier gave the asymmetrical form to the
whole knob, appears as a simple tube following down along the side of
the knob from the pedicel to the place of attachment of the sacculus, at
130 BULLETIN OF THE
the opposite end from its original junction. In the structure formed by
these changes we have the fully-grown condition of the complicated knob
of this Jelly-fish. (Pl. I. fig. 7.)
The resemblance of certain of the earlier stages in the growth of this
organ, or individual if one so designates it, to the adult in a different
genus is very great. Athorybva has a tentacular knob with many points
of resemblance to the undeveloped forms which have just been described.
The figures of the knob of this genus, as given by Gegenbaur, Kélliker,
and Huxley, show a close likeness to the younger stages of the knob in
Physophora.
While emphasizing this asymmetrical growth of the knob of the
young Physophora, and suggesting a likeness to the same structure in
the genus Athorybia, I recall the figures of the knob in the younger
stages of an Agalma, called by Leuckart Agalma clavatum. As Claus
suggests, this species is probably the young of Agalma Sarsit. Leuck-
art’s figures of A. clavatum show a knob which assumes a similar asym-
metrical shape to that which exists in the knob of Athorybia. . This
naturalist* has already made the comparison of a tentacular knob of
A. clavatum with the same structure in Athorybia. The comparison
seems to me a good one, and does not prevent a comparison of both
to the undeveloped tentacular knob of Physophora hydrostatica. A like-
ness is further indicated by the existence in each genus of terminal fila-
ments on the sacculus, provisional to be sure in Physophora, but none
the less definitely pointing out the relation of the structures under con-
sideration.t
II. The Mantle-Tubes of Apolemia uvaria and Gleba hippopus.
A wish to find out the homology of the somatocyst of the Calyco-
phores led me to a study of the chymiferous tubes of the swimming-bells
throughout the tubular Jelly-fishes. Especially in Apolemza and Gleba,
from their aberrant forms, I hoped to find some facts bearing on the solu-
tion of this question ; and when I came tosee the former of these genera
for the first time, my thoughts were turned to the question of its mantle-
tubes. This genus, in many respects allied to the Calycophoride, is a true
Physophorid; yet, in the published description of its nectocalyces, I find
no mention of any structure which, I think, can be truly known as the
* Siphonophoren von Nizza, Pl. XIII. Fig. 5, p. 91.
+ I find these structures in hydrostatica more leaf-like than they are represented in
Keferstein and Ehlers’s plate of Physophora Philippi.
MUSEUM OF COMPARATIVE ZOOLOGY. 131
mantle vessel. The four radial tubes of the bell, and the appendages to
the lateral pair, have been well figured and described. Leuckart seems
to liken rudimentary offshoots of the lateral vessels to mantle-tubes. I
do not think these offshoots more than very distantly comparable
with that special pair of vessels, which arises from a tube medially
placed in the bell, connecting the junction of the radial system with the
stem cavity of the animal. Such mantle-tubes, for instance, as are
to be found in Agalma, Gleba, or other genera, do not seem to have
been observed in the nectocalyx of Apolemza. I think, however, that I
have found in the bell of Apolemia a structure homologous to the man-
tle-tubes in the Physophoride, and represented in the Calycophore by
the somatocyst.
The mantle-tubes in Apolemza are difficult to make out, but seem to
differ only in their size from those in Gleba. Radial tubes in these
two genera, however, differ very greatly; for while in the one they reach
a development hardly equalled among Siphonophores, in Gleba, where
the cavity of the bell is very shallow, and the nectocalyx itself is more
of a bract than a swimming-bell, the chymiferous tubes have a mini-
mum development. So rigid is the nectocalyx of Gleba that the walls
admit of little motion, and most of the propulsion is done similarly to
that of Circe and other Trachynemide, by a movement of the velum,
a crescentic-formed vail surrounding the opening into the shallow bell
cavity. As a consequence, the radial system is quite diminutive in size.
Nowhere among Siphonophores better than in the genus Gleba do we
find a nectocalyx (PI. III. Figs. 4, 5), when fully grown, so closely resem-
bling a bract, and it seems to me that a better proof of the homology of
the central tube of the bract or covering scale with the mantle vessel
of a nectocalyx could hardly be desired.
Apolemia has a float and a true Physophorous nectocalyx,* while Gleba
has no float, and is radically different from the Calycophoride, although
its multiplicity of nectocalyces is a true characteristic of the Physopho-
ride. Therefore I think that the Hippopodidee should make one of
the three great groups into which the Siphonophore may be divided,
and be considered an equal division with the Physophoridz and Calyco-
phoridee.
* T figure (Pl. I. Fig. 1) a fragment of an Apolemia, without nectocalyx or float.
I have already published a representation of the nectocalyx of Apolemia. Proc.
Bost. Soc. Nat. Hist., Vol. XX.
132 BULLETIN OF THE
III. The Tubes in the larger Nectocalyx of Abyla pentagona.
The best description which I have found of the course of the chymif-
erous tubes of Abyla pentagona is by Gegenbaur.* At the regular meet-
ing of the Boston Society of Natural History, on November 5, 1879, I
pointed out the existence in Abyla of a supplementary tube, which takes
an origin from the junction of one of the radial vessels with the circum-
velar tube, and extends diagonally across one quadrant of the bell, ending
in an enlargement of a peculiar kind. I also indicated the difficulties
which present themselves to a determination of an homology between
the chymiferous tubes in Abyla and other nectocalyx-bearing Siphono-
phores, on account of these supplementary tubes. The bilateral sym-
metry shown quite well in the swimming-bells of other Calycophoride, as
Epibulia, Diphyes, and Praya, in the Hippopodide, and in Agalma, Agal-
mopsis, Halistemma, Apolemia, and Physophora of the Physophoride,
does not appear in the different spherorneres of Abyla. In all cases
except Adbyla, bilateral symmetry, as referred to a plane passing through
two opposite chymiferous tubes of the bell, and the ventral line of the
stem, is very easy to make out.. The want of symmetry in Adbyla is the
result of a covering in of the “ Lingskanal” by a growth from one of the
bounding ridges of the bell. A like covering of the canal is to’ be seen
in Monophyes, where the nectocalyx is hemispherical, with none of those
marked elevations and projecting points continued beyond the opening
of the bell which are so prominent in Abyla, and to which it owes both
of the specific names pentagona and trigona. I have noticed no varia-
tion from a normal arrangement of the chymiferous tubes in Monophyes.
(Pl. III. fig. 6.)
IV. On Halistemma, Agalma, and Agalmopsis.
The adoption of the generic name Halzstemma has now become almost
universal, and seems necessary for a proper understanding of the genera
of Siphonophores, about which there has existed considerable confu-
sion. The following animals have, I think, been erroneously placed in
this genus; viz. Halistemma tergestinum, Claus, and Halistemma carum,
Haeckel. Huxley, in ‘Oceanic Hydrozoa,” proposed the name for cer-
tain forms of tubular Jelly-fishes, with elongated axes, biserial rows of
swimming-bells, and naked tentacular knobs with a single terminal fila-
ment. The genus Agalma, by his classification, was to include those the
* Neue Beitrige zur Naheren Kenntniss der Siphonophoren. Nova Acta Carol.,
Vol. XXVII., 1860, pp. 349 - 356.
MUSEUM OF COMPARATIVE ZOOLOGY. lao
tentacular knobs of which had two lateral terminal filaments, while
Stephanomia had but a single filament of this kind, although the last
two genera have a biserial row of nectocalyces and an involucrum.
There are certain other characteristics of this genus which are not so
well marked as those already given by Huxley. I refer to the character
of the tentacles, and more especially to the position of the sexual organs.
Tentacles such as we find in Agalma do not seem to exist in the genus
Halistemma, but the tentacular knobs have very long pedicels, longer
than in other Physophoride, which allow the knob to project so far be-
yond the covering scale as to resemble tentacles very closely. Accord-
ing to some observers true tentacles do exist in the genus Halistemma.
For instance, Leuckart says that Kolliker missed the true tentacle, and
mistook the pedicel of the knob for a tentacle itselfi* Kolliker’s figure
of Agalmopsis punctata, which is the same thing as Halistemma rubrum,
shows the absence of the tentacles very plainly. My observations on the
tentacle agree with Kolliker’s, yet his figure of the animal is not com-
plete, in that he failed to represent the sexual system. The female
sexual organs I shall later describe. (PI. I. figs. 3-5.) Leuckart* fig-
ures a true tentacle in Halistemma. What Claus describes as Hali-
stemma tergestinumt does not seem to belong to Halistemma in the sig-
nification given to the generic name by its founder, Huxley. It belongs
rather to Huxley’s genus Stephanomia in all its structure, but especially
in the character of its tentacular knobs, a feature of greatest importance
in the classification of the Physophoride.
Haeckel (Entwickelungsgeschichte der Siphonophoren) proposes a di-
vision of the Agalmidz which has some advantages, although to use
the trifid character alone of the tentacular knob as a basis of his sub-
family Crystallodacea separates those with an involucrum, and places
Agalmopsis (Stephanomia, Huxley) with Forskalia and Halistemma.
These last have no involucrum in the tentacular knob, and the former
has sexual organs arising at the base of a polyp, while the latter has
these same structures midway between two tasters. There does not
* Leuckart, Zur Nahern Kenntniss der Siphonophoren von Nizza, Taf. XII. fig. 15.
When I studied Halistemma, I did not know of this difference of observation by
Kolliker and Leuckart.
+ 1. Metschnikoff, Proc. So. Fr. Nat. Moscow, Vol. VIII.; Studien der Medusen
und Siphonophoren, Zeitsch. f. Wiss. Zool., Bd. XXIV.
2. Claus, C., Ueber Halistemma Tergestinum, &c., Wien, 1878. Mittheilungen
uber Siphonophoren und Medusen Fauna Triests, Zool. bot. Gesell. Wien, Tom. XXVI.
3. Eschscholtz characterized the genus Agalma, ‘‘ Tentacula ramulis clavatis : clava
apice bicuspidata.”
134 , BULLETIN OF THE
seem to be sufficient ground for such a subdivision. I think it would
be better if all were placed with Athorybia, as separate genera, in the
Agalmidz, and no subdivision of the group of any other kind at present
attempted. /
In the Neue Beitrdge, Gegenbaur substitutes the name Stephanomia
for that of Yorskalia to designate a well-known form. He says, however,
nothing about the genera Halistemma and Agolmopsis, and neither
appears in his scheme of classification at the end of that work. Possibly
he considers both. as simply species of Agalma.
That which Claus in the last year (1879) has described and figured
under the name of Agalmopsis utricularia, ought to be a new genus
rather than a species of Agalma or Agalmopsvs.*
There seems no reason why the name Stephanomia, which Lesson ap-
plied to both Stephanomza contorta and Apolemia uvarva of later authors,
should designate the form with a biserial row of nectocalyces that it now
does. Apolemia (PI. I. fig. 1) is a well-marked genus. Leuckart adopts
the name Forskalia of Kolliker in his Siphonophoren von Nizza, and int
his Zoologische Untersuchungen applies the name Stephanomia to the
same genus. He rightly says of the so-called Porskalia that it was first
described by Milne-Edwards under the name of Stephanomia contorta
(Siphonophoren von Nizza, p. 93).
St. delle Chiaje’s use of the generic name, in a description of Stephano-
mia ophiura, although hardly accurate enough to be quoted in this dis-
cussion, should be mentioned. His designation of a species as ophiwra
is still retained in the nomenclature, and the form is easily to be known
from contorta, from which even the fishermen of Messina distinguish it,
although they affix to both a characteristic name, “ Pinie di Mare.”
Kolliker (Siphonophoren von Messina, p. 18) says that Lesson is
wholly in error, ‘Wenn er die Stephanomia contorta und prolifera von
Milne-Edwards zu derselben (Apolemia uvaria) zieht.” In the Nachtrag
to the same work he says: ‘“‘Immer hin bleibe ich bei dem Genus For-
skalia das nach einem vollstandigen Thiere gebildet ist und kann der
Name Stephanomia fiir das nur unvollstiindig bekannte Thier bleiben
fiir das er von Peron zuerst aufgestellt wurde.” The ‘ unvollstandig
bekannte Thier” was that same form whose anatomy Huxley later pub-
lished under the name which Peron gave it, although he says that
Peron’s sketch has “no scientific value.” What animal Peron had will
* Claus, Agalmopsis utricularia eine neue Siphonophore des Mittelmeeres, Arbei-
ten aus dem Zoologischen Instituts der U. Wien und der Zoologischen Station in
Triest, Bd. II. 2 Heft.
x MUSEUM OF COMPARATIVE ZOOLOGY. 135
always remain problematical, and there is no good reason to identify the
form studied by Huxley with it.
In the Grundziige der Zoologie, 3 Auf., p. 237, Claus includes in the
family of Agalmidz Forskalia (Stephanomia, M. E.), Halistemma, and
Agalmopsis. He, like Haeckel, mentions Vanomia cara as a species of
Halistemma, and says that Stephanomia (Peron) is included in the same
genus. Packard follows Claus in this reference of Vanomza to Hali-
stemma. .
In Nanomia cara, the first formed structure in the larva, according to
Mr. Alex. Agassiz, is the float, as in Agalmopsis (Stephanonua, Metsch.).
In Halistemma, according to Metschnikoff, the swimming-bell and float
develop together from the very first. Although it is possible that the
float is simply a modified Medusa bell or nectocalyx, no one would mis-
take the young of Halistemma for that of a Vanomza larva. As Metschni-
koff has already pointed out, Vanomia in its younger stages resembles
the genus Agalmopsis* (Stephanomia, Metsch.). Huxley’s classification
of the Siphonophore, with a verbal change, is the best which has been
proposed as far as the Agalmide are concerned. We can retain the
three generic names Agalma, Agalmopsis, and Halistemma. That would
keep Eschscholtz’s genus to designate & Physophorid with a trifid tentacu-
lar knob, the Agalmopsis of Sars with a single terminal filament on the
same structure, and Halistemma, a form the tentacular knobs of which
do not have involucra, and the tentacle is replaced by the pedicels of the
tentacular knobs. In addition to the genera Agalma, Agalmopsis, and’
Halistemma, I would include Athorybia among the Agalmide, on account
of its embryonic likeness to Agalma. It may possibly be simply the
young of this genus. The only other Physophorid, except Stephanomia
(Yorskalia), where we have a multiserial necto-stem, is Physophora tetra-
* Notwithstanding Sars figures three radically different kinds of knobs in his
genus Agalmopsis, a condition only observed, with this exception, in Rhizophysa and
the larval forms of certain Agalmide, his figures 5, 6, on Plate V. are among the
earliest, if not the first, representations of a tentacular knob with an involucrum and
a single terminal filament. I retain, therefore, the name which he has given for the
Jelly-fish with this characteristic, particularly on account of the exact use of Stepha-
nomia by Milne-Edwards (Ann. d. Sci. Nat. 1841, Tom. XVI. p. 217). See also
Leuckart’s note, Siphonophoren von Nizza, p. 93 ; and Huxley, Oceanic Hydrozoa ;
Sars, Fauna Littoralis Norvegie, 1846. In Middelhavet’s Littoral Fauna, where
all descriptions of Siphonophores are simply numbered, and with no subdivision,
Agalma rubrum (A. punctatum, Koll.) is followed directly by Agalma Sarsii, a
species with a trifid tentacular knob. In that work Sars makes no mention iof the
genus with a covered (by an involucrum) tentacular knob and a single terminal
filament.
136 BULLETIN OF THE
stica of Philippi (Miiller’s Arch., 1843). Leuckart thought (Stphonophoren
von Niza, p. 106, note 2) that this species ought to be made a new
genus. I have not found the form redescribed by any naturalist since
Philippi, and, although I have frequently taken Physophora hydrostatica
and Philippi in my excursions on the Mediterranean, I have never seen
tetrastica. Gegenbaur’s view, to which Keferstein and Ehlers also in-
cline (Zoologische Beitrage, p. 30, note 7) seems a good explanation of the
apparently multiserial arrangement of nectocalyces spoken of by Philippi.
Gegenbaur suggests that this multiserial character of the necto-stem in
tetrastica is brought about by an accidental twisting of the necto-stem, a
thing which often happens in Physophora, Agalma, and Halistemma. An
Agalma which answers to Leuckart’s description of A. clavatum was found
in such numbers as to give me almost a perfect series between it and
Agalma Sarsw. It was not possible, however, for me to raise the lat-
ter from the former, but the evidence which have mentioned seems
enough to prove the identity of the two. Claus * has already made a
similar suggestion. I have frequently taken at Villefranche a Jelly-fish
identical, I think, with that which has been described by Claus as Hali-
stemma tergestinum, and by Metschnikoff as Stephanomia pictum. A
description of this animal, which I had formerly thought new to science,
I had prepared without any intimation of the previous work of these
naturalists. S. pictum was taken by Metschnikoff from the same locality
where my studies were made. I think from the character of the ten-
tacular knobs that we have in this interesting Siphonophore a true Agal-
mopsis as I have limited the genus, or a Physophorid with an elongated
stem, no part of which is enlarged into a sac as in Physophora, and
which is furnished with only a biserial row of nectocalyces. In addi-
tion it has a tentacular knob possessing an involucrum and a single
filament. Metschnikoff’s change of the Jelly-fish described by him, which
is probably the same, from the genus /alstemma, to which he at first
referred it, to the genus commonly known as Stephanomia, was well
made.
The feature which distinguishes Agalmopsis (Stephanomia, Metsch.)
picta from Halistemma, together with those already mentioned, is the
position of the sexual organs (Pl. I. figs. 1, 3, 6), and, less definitely,
the small size of the covering scales as compared with the nectocalyces.
The crimson and orange sexual organs in /. tergestinum, as Claus
figures them, and as I have also observed, are clustered, both male and
female, at the base of a taster (Pl. I. fig. 6), the male mounted on an
* Zeitsch. f. Wiss. Zool., Bd. XII. p. 559.
MUSEUM OF COMPARATIVE ZOOLOGY. 187
especial stalk, and not separated from the taster, as in H. rubrum. The
bracts are small, and so transparent that at first sight one is inclined to
doubt their existence in Agalmopsis picta, while in Halistemma they are
large and conspicuous. This feature effects very considerably the rela-
tive forms of the two Jelly-fishes.
All along the necto-stem and polyp-stem of Agalmopsis picta, more
especially, however, upon the former, there are to be found in the ecto-
derm, as Claus has already mentioned, bright crimson pigment spots
more clearly marked than is generally the case with similar spots on the
stem of other Siphonophores. Two of these pigment spots, together
with a finger-like process near them, also exist on the young nectocalyces.
In very young swimming-bells there are three of these pigment spots.
They occupy a position similar to that of the pigment spots of other
hydroid Medusee, at the junction of the lateral and superior * tubes with
the circumvelar vessel. There are very interesting highly refractile red
spots of a problematical function covering the bracts in Agalma Sarsit
and Agalma clavatum. (Pl. I. fig. 2.) These bracts, from the place of
attachment and the twisting of the stem, form a well-marked spiral
around the polyp stem of the animal. The spots on each side of a cen-
tral line are arranged on every scale in irregular rows, extending longi-
tudinally across the bract, each pigment spot being enclosed in a cell.
These peculiar pigment spots of the covering scales, represented remotely
also in some genera, as in Apolemia (Pl. I. fig. 1), by elevations com-
posed of clusters of cells on the surface of the bract, are the most ap-
parent structures in the transparent bract of 4. Sarszz, since with that
exception there is hardly any coloration in the covering scale. In A.
clavatum, the sexually mature young of A. Sarszz, only four rows of these
pigment spots occur, as Leuckart has shown. When the bracts which
bear these paralleled rows of spots are detached from the axis, their
color changes to a yellow, and a fluid of the same color exudes into the
surrounding water. I have not been able to find any mention of this
rupture of the cell wall and discharge of a yellow fluid when the bract
is detached, in the descriptions by other naturalists. I think these
scale cells belong to the ectodermic layer.
* A nomenclature of the different spheromeres of the nectocalyx of a Siphonophore
would simplify a description of the bell. As paired chymiferous tubes opposite each
other have resemblances in their course from their relation to a plane passing through
the dorsal and ventral line of the stem, they may be called lateral tubes, and the
respective sections of the bell in which they lie, lateral spheromeres. The remaining
spheromeres, according to their position in relation to a float, where such exists, may
be called the superior, or the inferior, corresponding with a proximal and a distal.
138 BULLETIN OF THE
The pigment spots mentioned in the nectocalyx of Agalmopsis picta
have no resemblance to these peculiar bodies on the bracts, nor do they
change their color when the swimming-bell is detached. The presence
of such spots on the younger bell of Agalmopsis picta, and so little devel-
oped on the adult, rank them among patterns of embryonic coloration,
examples of which are not unknown on other structures of these animals.
Stephanomia * (Forskalia) has a similar large yellow spot, which persists
in the adult nectocalyx, at the junction of radial and circular tubes.
The different stages in development of the female sexual organs of
Halistemma have never been described or figured. Kolliker,t in his
plate illustrating this genus, does not even represent these parts, and
Leuckart} figures the female organs as a botryoidal structure, at the apex
of a single polyp-like stalk. In several specimens, in addition to a struc-
ture of this kind, we have, as I have figured (Plate II. Fig. 3), others
with the stalk on which the botryoidal mass is borne bifid at its extrem-
ity. This is probably simply another stage in development of these
organs. As Leuckart well says, the sexual organs in Halistemma have
no direct connection with the tasters; still, the female structures, at
times, arise very near them.§
* The single yellow pigment spot at the junction of radial and circular tubes in
Stephanomia (forskalia) has on each side a finger-like process, and also, separated
from these only by a short distance, an additional pair of the same rudimentary ten-
tacles, as they may be called. The pigment spot is mentioned by Kolliker, who also
calls attention to one pair of these tentacles or processes. He says: ‘‘ Der Pigment-
fleck ist insofern interessant als bei keinerandern Siphonophore Pigmentirungen de
Schwimmglocken beobactet wurden.” (Schwimmpolypen von Messina, p. 4.)
+ Kolliker, Schwimmpolypen von Messina, Tab. IV.
+ Leuckart, Zoologische Untersuchungen, Tab. II. fig. 14 ; Siphonophoren von
Nizza, Tab. XII. fig. 15.
§ Claus says (H. Tergestinum, &c., p. 45) : ‘Wo man bei verwandten Agalmiden
die Sprossung der Geschlechts-traubchen am Stamme beschreiben findet representirt
entweder der Stiel des Tréaubchens einen Taster dessen Endabschnitt kurz und ver-
kiimmert bleibt oder aber der Tasterschlauch hat sich von Stiele gelost und ist abgefal-
len.” The resemblance to a taster of the stalk upon which the botryoidal female organs
of Halistemma are borne, is very small. However, in Agalmopsis and Stephanomia
(Forskalia) we find the sexual system at the base of the true taster, which seems to
support Claus’s suggestion. Huxley, who had not seen the genus Halistemma when
‘Oceanic Hydrozoa ” was written, says of reproductive organs that they are like those
of Stephanomia, and are attached directly to the ccenosarc. The sexual organs have
no similarity in point of attachment, as can be seen from my figures of these two
genera (PI. II. figs. 1, 3) ; for while in the case of Halistemma they arise directly
from the stem, in Agalmopsis (Stephanomia) they are united to the base of the taster.
x
MUSEUM OF COMPARATIVE ZOOLOGY. 139
V. Notice of a few Siphonophore and Velellide from the East-
ern Coast of the United States.
Up to the present time few forms of either of these groups of Jelly-
fishes have been described from the waters of our bays and sounds.
They seem to be only occasional visitors, blown into the neighborhood
of-our shores from mid-ocean, or brought there from the tropics by the
Gulf Stream. The wealth of tubular Medusz which one finds in the
Mediterranean is unknown on New England coasts or in Charleston
Harbor, localities in which these animals have been best studied. Upon
many single excursions on the quiet bays near Nice, in Southern France,
I have taken eight different genera of Siphonophore ; but their rarity is
so great at Newport that seldom have more than one or two genera
been taken by me in the same day ; and a whole summer, in which I was
almost daily upon the water, has passed without the observation of a
single genus. A similar case of absence of all pelagic animals happened
at Villefranche, last November. In that month, although I was on the
water daily, I observed not only no Siphonophores, but also none of those
Heteropods and Pteropods which later appeared in such numbers. Certain
of the Siphonophore, however, are more abundant with us than in Ville-
franche, Naples, or Messina. Physalia caravella is now rarely taken in
numbers by naturalists at either of these stations; but many examples
of Physalia arethusa may be found almost any summer in Vineyard Sound
or the entrances to Narragansett Bay.
The well-known Physalia arethusa is the most common of New Eng-
land Siphonophores. It was long ago described by one of the pioneers
in the study of Jelly-fishes, and later beautifully figured by Prof. Agas-
siz in the Contributions to the Natural History of the United States.
Prof. McCrady* describes a form, Physalia aurigera, which is consid-
ered by Mr. Alex. Agassizf as the same species. In the Catalogue of
the North American Acalephe, the list of places from which speci-
mens of Physalia arethusa had been taken includes localities all the way
from Cape Cod to Florida, and beyond in the West Indies.
The two floating Hydroids, Veledla and Porpita, so closely allied to the
Tubularians and known as the Velellide, are also found in our waters.
The problematical genus Rataria,t by some supposed to be the young
of Velella, in swarms of which it is generally found, and by others an
immature Porpita, I think has not been described from our coast. I
* Gymnopthalmata of Charleston Harbor, 1857.
+ North American Acalephex, 1865.
+ Pagenstecher, Zeitsch. f. Wiss. Zool., Bd. XII., 1863.
140 BULLETIN OF THE
find no mention of it from New England waters. According to Agas-
siz, our Velella is Velella mutica of Bosc. Of that identification there
seems no doubt, considering where the animal which Bose described was
found ; but, as Pagenstecher* and Delle Chiaje suggest, it is difficult to
see exactly what Bosc meant by his other species, tentaculata. The for-
mer of these authors says Bosc called the Veledla of Linné and Lamarck
mutica, while the species spurans of Forskal received the name tentacu-
lata. Mr. Alex. Agassiz mentions a V. septentrionalis from our Pacific
coast. Some of the material for the earliest descriptions of the Siphono-
phorze and Velellidze was collected in the Pacific Ocean, and near our
western shores, and we should naturally expect these species taken by
early voyagers from those localities.
Porpita I have never seen alive in our waters, but have a dried speci-
men preserved on paper after the manner of a plant, taken by a sailor
not far from Nantucket. Prof. McCrady describes a species of Por-
pita from Charleston Harbor, not very different from Guilding’s Porpita
(Polybrachionia Linneana), which he calls Porpita Linneana. He is
inclined to think it a new species.
The only known member of the long-stemmed Siphonophore, provided
at one end with a float or air-bladder, which has been described from
New England waters, is Agalmopsis cara (Nanomia cara, A. Ag. ; Ste-
phanomia cara, Metsch.; Halistemma carum, Haeckel, Claus, Packard,
and others). This animal was first described by Mr. Alex. Agassiz,
to whom we owe so much of our knowledge of the Jelly-fishes of our
waters. The drawings and descriptions of the development which he
gives are not only the earliest of this particular genus, but, with those of
Claus, Leuckart, Kélliker, and Gegenbaur, of the embryology of the
Siphonophoree as a whole.
As I have already said, Haeckel considers Nanomia cara a species of
Halistemma, and places it under this genus in his table of the Agalmide.
He seems to have been followed by Claus, who adopts the name /7/. carum
in his Grundziige der Zoologie. When Mr. Agassiz described the form he
said it was closely related to Agalmopsis as well as Halistemma, but that
the mode of arrangement of the swimming-bells and the nature of the
tentacles of the feeding polyps show undoubtedly that it cannot be placed
in the same genus as Agalmopsis, having in mind Sars’s genus. Wanomia
cara, according to Metschnikoff, as already shown, should be regarded
as a species in the genus Stephanomia. The reason for his conclusion,
he says, is on account of the resemblance between the larve as figured
* Pagenstecher, Zeitsch. f. Wiss. Zool., Bd. XII., 1863.
MUSEUM OF COMPARATIVE ZOOLOGY. 141
by Mr. Alex. Agassiz and Kowalevsky. He says: “Die Aelteste von
Kowalevsky gezogene Larve mit Luft apparat Magen und Fang faden
gleicht so sehr dem jungsten von Alex. Agassiz gefangenen Jugendzu-
stande der Nanomia, dass es mir sehr wahrscheinlich ist, dass auch diese
Physophoride in die Gattung Stephanomia eingezogen werden muss zumal
zwischen beiden eine grosse anatomische Analogie besteht.” The absence
of the cap-shaped provisional bell in the very young Manomia shows
that it does not belong to the genus Agalma, and the fact that a float
and not a nectocalyx is first developed, separates it from Halistemma.
Metschnikoff’s conclusion seems to me the most natural one. I there-
fore would refer it to the genus Agalmopsis, of which I regard Stepha-
noma, as ordinarily used, a synonym.
There are certain points in which, following the description by Mr.
Alex. Agassiz (North American Acalephe, pp. 200 - 213), Vanomia differs
from the other related Siphonophorz which I have studied. He says
that the float in this genus contained a globule of oil. I have never
seen the genus fully grown in our waters, and can only judge from my
studies of most of the other genera of the justness of Metschnikoff’s
criticism (Studien der Medusen und Siphonophoren, p. 36) of Alex.
Agassiz on this point. If the float does contain oil, I think it an excep-
tional case among Siphonophores.
The second kind of feeding polyps, as described in Nanomua, are, I
believe, simply immature forms of the first, and the tightly-coiled cork-
screw parts are only undeveloped tentacular knobs. I have often found
the young knobs of Agalma Sarsw and A. elegans clustered in the same
manner at the base of a feeding polyp before a true tentacle had been
formed. ;
The resemblance of the tentacular knob of Nanomia, with its ‘ cnido-
fils,” as shown in Mr. Agassiz’s drawing (Fig. 339), to the provisional
structures bearing the same name in Agalmopsis picta and the “ Athory-
bia stage” of Agalma, is very great. This likeness is a very interesting
fact, indicating either an embryonic condition of the adult of Nanomia, or
that it is the larval form, sexually mature, of another Siphonophore.
The origin and earlier development of Vanomza cara, according to Mr.
Agassiz, as a bud from the stem, is, I think, exceptional. In those other
Siphonophores whose development is more or less completely known
through the studies of Claus, Haeckel, Kowalevsky, and Metschnikoff,
we find only an egg development of the new colony.
Dana describes (Mem. Amer. Acad., Vol. II. Part I.) a Physophorid
from the Pacific Ocean. He calls it Crystallomia polygonata. The
147 BULLETIN OF THE
figures which he gives of the tentacular knob seem to show that it is the
genus Agalma of Eschscholtz. Haeckel refers it to his genus Crystal-
lodes. The whole embryological history of Agalma and Crystallodes, with
the exception of the appearance of a yolk-sac in the latter, according to
Haeckel, as Metschnikoff says, is very much the same. Dana published
his description in 1857, two or three years after the great works by the
German naturalists on the Siphonophores of the Mediterranean.
I know of two genera of Leuckart’s Calycophoride, a group of Siphono-
phores, which appears to me well defined, which have been described
from our eastern coasts. In his ‘ Gymnopthalmata of Charleston Har-
bor,” Prof. McCrady describes and figures a new diphyozoid, which
he names Ludoxia alata, and a new Diphyes, D. pusilla. His Hudoxia
alata seems to be the same as /. Lessonw of Huxley. This animal, ac-
cording to this prominent English naturalist, is the diphyozoid of D.
appendiculata, » synonym of Leuckart’s D. acuminata. The mention
which Prof. McCrady makes of Diphyes pusilla is too short to be of ser-
vice in distinguishing it from Mediterranean Diphyide. A figure of a
Diphyes acuminata from Villefranche may have some interest, especially
as its diphyozoid, Hudoaia Lessoni, has been found by me at Newport.
Leuckart mentions in his Siphonophoren von Niza an EHpibulia (Galeo-
laria), given him by Philippi, and taken from the coast of Greenland.
To the Siphonophorous fauna of eastern coasts of North America® I
can add a new member of the Agalmide, probably the same as Sars’s
Agalmopsis elegans, and the two diphyozoids, Hudoaia Lessona and Diplo-
physa inermis. There is a great diversity of opinion among naturalists
what Diplophysa is. All seem to be united in the opinion that it is a
diphyozoid, but there is an unanswered question of what Calycophore it
is the fragment. I mention a few of the opinions. Gegenbaur,t who
first described the form, seems to think its resemblance not very dis-
tinct from Lrsea truncata of Will. On page 366 of his Neue Beitrdge
he says that “Sie (Diplophyse) entsprechen in der Sculptur der Diplo-
physen-gattung Praya.” Praya is probably the same as Ersea. Huxley _
(Oceanic Hydrozoa, p. 66) says that Diplophysa inermis has some resem-
blance to the diphyozoid Cucubalus described by Quoy and Gaimard, but
says he was unable to arrive at any definite opinion as to what animals
were included by the French voyagers in their genera Clymba and Cucu-
balus.
* My observations on American Siphonophores were made in the laboratory of Mr.
Agassiz, at Newport, R. I.
+ Beitrige zur niiheren Kenntniss der Schwimmpolypen (Siphonophoren).
MUSEUM OF COMPARATIVE ZOOLOGY. 143
The title of one of Claus’s valuable papers on the Siphonophore is Die
Gattung Monophyes und thr Abkimmling Diplophysa, in which he sup-
ports the idea that Diplophysa is a diphyozoid of Monophyes gracilis, Cls.
He makes Huxley’s genus Spheronectes a synonym of Monophyes. He
repeats in his Grundziige der Zoologre, 3 Auf., 1876, that Diplophysa
tnermis is a diphyozoid of Monophyes gracilis, as stated above.
Metschnikoff (Studien tiber die Medusen und Siphonophoren, p. 46)
says, concerning the relationship of these animals, that fragments of the
form Praya mermis were described by Gegenbaur as Diplophysa inermis.
He bases his idea of the relationship of these two genera on the identity
of the larva of Praya, which he describes, with the remarkable genus
of Gegenbaur, and more especially on the resemblance in the form of
their nectocalyces. He adds also, that both genera are of small size,
which cannot, if taken alone, be a very strong argument for their
relationship.
¢
VOL. VI.—NO. 7. 2
144 BULLETIN OF THE
TABULAR LIST OF VELELLIDA AND SIPHONOPHORA,
FROM THE EASTERN COAST OF THE UNITED STATES.
VELELLIDA,
Velella mutica, Bosc.
Acassiz, L., Cont. Nat. Hist. U. 8., Vol. IV. p. 366, 1862.
Agassiz, A., North American Acalephe, p. 216, 1865.
Velella spvrans.
V. tentaculata (2), Bosc.
Porprta Linneana, LEss.
McCrapy, Gymnopthalmata of Charleston Harbor, 1857.
Agassiz, A., North American Acalephe, 1865.
Porpita gigantea.
FEWKES, Nantucket.
SIPHONOPHORA.
I. Physophoride.
1. AGALMIDA.
Agalma elegans, FEwKrs, Newport.
Agalmopsis elegans, SARS, Fauna Littoralis Norvegie, 1846.
Agalmopsis (sp. 1).
Nanomia cara, Acassiz, A., North American Acalephe, 1865.
Halistemma carum, HAECKEL, Ent. d. Siphonophoren. »
Stephanomia cara, METSCHNIKOFF, Zeitsch. f. Wiss. Zool., Bd. XXIV., 1874.
2. PHYSALIDA.
Physalia arethusa, TIL.
Agassiz, L., Cont. Nat. Hist. U. S., 1862.
Agassiz, A., North American Acalephe, 1865.
Physalia aurigera, McCravy.
Mr. Agassiz suggests that this is the same as Physalia arethusa of Tilesius,
II. Calycophoride.
1. DIPpHyID&.
Diphyes acuminata, Luck. The diphyozoid of this Siphonophore is Zudoxa
campanulata,
MUSEUM OF COMPARATIVE ZOOLOGY. 145
Eudoxia campanulata, FEwKES, Newport.
Eudoxia Lesson, HuxtEy, Oceanic Hydrozoa.
Eudoxia alata, McCrapy, Gymn. of Charleston Harbor.
Diphyes pusilla, McCrapy, Gymn. of Charleston Harbor.
2. PRAYIDA.
Praya inermis has, according to METSCHNIKOFF, the diphyozoid Diplophysa
inermis (GEG.).
Diplophysa inermis, FEwKES, Newport.
In this incomplete list of tubular Jelly-fishes, we miss many of those beautiful
forms which are so familiar to the naturalist on the Mediterranean. Extended
observations in our Southern bays will probably bring to light the well-known
Siphonophores common to all oceans, Apolemia, Abyla, Physophora, and
Gleba. Some of these have already been taken in the Gulf of Mexico and
Caribbean Sea. Rhizophysa, found in the same localities, may also be ex-
pected, brought by ocean currents to our coasts.
CAMBRIDGE, April 1, 1880.
146 BULLETIN OF THE MUSEUM OF COMPARATIVE ZOOLOGY.
EXPLANATION OF THE PLATES.
a, float; b, nectocalyx; c, necto-stem; d, polyp-stem ; e, feeding polyp; jf, taster;
g, ovaries; h, testes; 7, tentacle; 7, tentacular knob; a, involucrum; 8, sacculus;
7, pedicel; 5, terminal filaments; X, tentacle of the taster; 7, somatocyst; n, radial
tubes; 0, circular vessel; p, covering scale; qg, longitudinal canal; ec, ectoderm;
en, entoderm; 7, joint in polyp-stem; s, nectocalyx of diphyozoid ; ¢, crescentic-
formed velum in Gleba.
The mantle-tubes, somatocyst, and central tube of the bract or covering scale are
designated by the letter 7. They seem to be the same structures.
PLATE I.
Fig. 1, Apolemia uvaria, a part of the polyp-stem, magnified four diameters. The
longest stem observed by me was eight feet in length. Figs. 2, 3, 4, 5, 6, 7, different
stages of development of the tentacular knob of Physophora hydrostatica. Fig. 3
shows the origin of the involucrum. Fig. 4, 5, 6, represents the provisional form of
the knob, and the embryonic terminal filaments. Fig. 7, a knob in the most developed
condition.
PLATE Ii.
Fig. 1, view of Agalmopsis picta from one side, magnified two diameters. The ten-
tacles are drawn to the vicinity of the polyp-stem by which the tentacular knobs
appear on the upper side of that appendage (an unusual condition.) Fig. 2, covering
scale of Agalma Sarsit. Fig. 3, portion of the polyp-stem of Halistemma rubrum,
magnified four diameters. Fig. 4, tentacular knob of Halistemma rubrum. The
lower extremity of this figure joins figure 3 at the point y. Fig. 6, taster of Agal-
mopsis picta. This figure shows the position of the male and female organs in refer-
ence to the taster.
PLATE III.
Fig. 1, Praya diphyes. Fig. 2, Praya, sp. (?) This unknown species of Praya
differs from Praya cymbiformis in the equality in size of the nectocalyccs, their tri-
angular outline when seen in profile, and the direct course from junction to circular
vessel of the radial tubes. The difference between it and Praya diphyes is plainly
brought out by the accompanying Fig. 1. It has the somatocyst in but one necto-
calyx, and the diphyozoids are crowded together along the polyp-stem, somewhat
similar to the conditions among the Agalmide. I incline to regard Fig. 2 as the
young of Praya cymbiformis. Fig. 3, Diphyes acuminata. Fig. 4, lateral view of
the nectocalyx of Gleba hippopus. Fig. 5, inferior view of a similar nectocalyx.
Fig. 6, Spheronectes (Monophyes) inermis. All these drawings are from Jelly-fishes
taken in the Mediterranean.
e
5.
»>
SNE,
m Boston
Tue Heuiotype Printino Co. 126 PEARL 8
Piate IL.
re Sse
E Aad ANS:
E | AN es
fe
he Ny)
IWF
Tue Hevioryps PRintina Co. 126 PEart Sn Boston
Tae Hevoryee Pruvrina Co. 126 Peart Sr. Boston
Plate Jil.
No. 8.— (Letrer No.4.) Zo Caruite P. Patrerson, Superin-
tendent United States Coast and Geodetic Survey, Washington,
D. C., from ALEXANDER AGASSIZ, on the Dredging Operations
carried on during part of June and July, 1880, by the United
States Coast Survey Steamer “ Blake,” Commander J. R. BARTLETT,
. Ss.
I gomneD the “Blake,” at Newport, late in June. According to your
instructions, we proceeded to the northeastern edge of George’s Shoal,
where we ran our first line of dredgings from the 100-fathom line to a
depth of nearly 1250 fathoms. Our second line was run to the south-
east, off Montauk Point. This was interrupted by bad weather. We
were compelled to put into Newport, and completed the line on our
return from the South. This line extended to nearly 1400 fathoms.
On leaving Newport for the second time we steamed directly. for
Charleston, 8. C. A line of dredgings was run from the 100-fathom
line normal to the coast directly across the Gulf Stream to a distance of
about 120 miles to the eastward of Charleston. Finding that our depth
did not increase at that distance, — our greatest depth not being much
more than 350 fathoms, — Commander Bartlett thought it prudent to
return towards shore, to the so-called axis of the Gulf Stream, and to
run a line in a northeastern direction parallel to the coast in the trough
of the Gulf Stream. To our great astonishment the depth did not in-
crease. We carried from 250 to less than 300 fathoms until we nearly
reached the latitude of Cape Hatteras, when in a short distance there
was a very rapid drop from 352 fathoms to 1,386 fathoms. A fifth line
was run normal to this northern slope of the Gulf Stream plateau, to a
depth of 1,632 fathoms. A sixth line was run to the northward of Cape
Hatteras, to a depth of 1,047 fathoms. A seventh line was run east off
Cape May, from the 100-fathom line to nearly 1200 fathoms.
We were greatly disappointed in the richness of the fauna on the
lines off Charleston and in the Gulf Stream, owing partly to the very
gradual slope of the continent towards deep water, and the strong cur-
rent of the Gulf Stream, which sweeps everything off the bottom along
its course., There is but little food for the deep-water animals, and it
was only along the edges of the Gulf Stream where mud and silt accu-
VOL. VI. — NO. 8.
148 BULLETIN OF THE
mulated that we made satisfactory hauls on our Southern lines. What
was obtained seemed to be a scanty northern extension of tht fauna of
the Caribbean Sea and of the Gulf of Mexico between the 100 and 350
fathom lines. It was not until we trawled on the steep slope of the
Gulf Stream plateau south of Cape Hatteras, where the bottom was fine
mud and Globigerina ooze, that we made a rich harvest again, in striking
contrast to the poor hauls along the well-swept rocky or hard bottom of
the Gulf Stream to the southward. Along the western edge of the Gulf
Stream we came upon several patches of the modern green-sand forma-
tion, where the bottom was entirely composed of perfectly clean dead
Globigerinee. Although Pteropods were very common at the surface all
the way from Charleston to Cape Hatteras, they were only rarely brought
up dead from the bottom ; but when the steep slope south of Hatteras
was reached they again assumed a prominent part in the composition of
the bottom mud.
While running the line parallel to the coast from off Charleston to
Cape Hatteras, we came twice upon localities where the sounding cup
brought up nothing but clean Globigerine, the bottom consisting en-
tirely of the modern green-sand to which Bailey and Pourtales had
already called attention as forming off shore on the Atlantic coast of the
United States. The rapid changes in the character of the mud, as we
increase both our distance from shore and the depth, are well shown in
the nature of the bottom of the different depths along the short, steep
line forming the northern slope of the Gulf Stream plateau traced by the
“Blake” from Charleston to south of Cape Hatteras. We very rapidly
pass from the comparatively coarse mud to fine and finer ooze, which
becomes an impalpable silt in the deeper water beyond 1,000 or 2,000
fathoms, assuming at the same time gradually a lighter color.
Among the Tunicates I may mention two new species of Salpz, one
of which is interesting, its chain occupying an intermediate position
between that of Salpa pinnata and the ordinary Salpa chain of 8. zo-
naria or S. Cabotti of our coast. The solitary individuals are gigantic
specimens, measuring no less than twelve inches in length. This solitary
form is closely allied to S. maxima, but differs from it in the number
and arrangement of the muscular bands. The chains grow to a great
length, some of them measuring more than ten feet in length and as
much as nine inches in breadth. The zodids are arranged as in S. pin-
nata, side by side in a single row, extending vertically across the whole
width of the chain, and forming a thin ribbon, which when floating is
usually slightly coiled like a tape. The zodids of the chain resemble
MUSEUM OF COMPARATIVE ZOOLOGY. 149
S. Africana. This species was found at sea from Cape Hatteras as far
north as the eastern extremity of George’s Shoal.
Among the Acalephs, the most interesting form was a species of Do-
decabostricha, Br., the largest specimen measuring no less than nine
inches in height. Several specimens of a dark violet (claret-color) were
brought up in the trawl, and it is very probable from the systematic aftin-
‘ities of this Medusa that, like its allies, the Rhizostome, it lives on the
bottom, rarely coming to the surface. For the genus Dodecabostricha
Professor Agassiz established a new family, the Brandtidze, and placed it
in the vicinity of the Charibdeide. While it undoubtedly has a general
resemblance to the Charibdeide, the structure of the genital pouches
and of the lobes of the actinostome shows that it is intermediate between
the Aurelie and the Rhizostome proper, combining at the same time
structural features only found in the Pelagiz. It is not known where
Mertens found the species which is figured in Brandt’s memoir. As
we trawled mainly on mud or clay bottoms, but few Hydroids were col-
lected.
All along the course of the stream we found large quantities of Tri-
chodesmium erythreum. On one occasion, north of Hatteras, we passed
through an extensive patch of this pelagic Alga, which colored’ the
surface of the sea a dirty yellow for a distance of about a quarter of a
mile by a hundred yards in width.
Among the corals a fine species of Flabellum, probably the Flabellum
alabastrum, Mos., and a few species characteristic of the West India seas
and of the Gulf of Mexico were found to extend as far north as Cape
Hatteras. There were a number of Pennatule and Virgularie collected,
probably the same species already described by Professor Verrill from the
collections made by the United States Fish Commission, as well as a few
Gorgoniz, among which I may mention numerous specimens of Kera-
toisis. The Pennatulz and Gorgoniz were all remarkable for their bril-
hant bluish phosphorescence, a single Pennatula lighting up a large tub
of water. A couple of species of Zoanthus were found in deep water.
Among the Actinic large specimens of Bunodes and of Edwardsiz came
up from depths of from 600 to 800 fathoms.
Among the Echinoderms all the way from Cape Hatteras to the ex-
tremity of George’s Shoal, Ophiomusium Lymani were quite common
in deep water. Kchinus norvegicus is abundant, and Schizaster fragi-
lis extends from deep water inside the 100-fathom line. A species of
Asthenosoma and one of Phormosoma were also found in deep water,
having the same general distribution as Ophiomusium. A fine species
150 BULLETIN OF THE
of Urechinus closely allied to Urechinus naresianus, and several of the
rarer species of Starfishes, — Archaster, Porcellanaster, Luidia, Astro-
gonium, Porania, Pteraster, and Hippasteria, — were found to extend
far into deep water; and beyond 1,000 fathoms, off George’s Bank,
we found several fine specimens of Brisinga, as well as three or four
species of the remarkable deep-sea Holothurians belonging to the or-
der of Elasmopoda; among the Crinoids, Comatula Sarsii? and a few
specimens of Rhizocrinus. Although the line to the eastward of Charles-
ton, S. C., was commenced off the very home of the Scutellz and other
Clypeastroids, it is remarkable that not a single Mellita or Clypeaster
was dredged up, either on that line or the line run in the axis of the
Gulf Stream as far as Cape Hatteras. LEchinarachnius off George’s Shoal
was found to extend to a much greater depth, living specimens having
come up in the trawl from a depth of 524 fathoms. |
But few Annelids were collected, a few specimens of Nemerteans, and
of Calymne; one of the large Eunicide, the tubes of which, sometimes
fully fifteen inches in length, often filled the bottom of the trawl when
dragging on muddy bottoms, was specially numerous.
A number of species of Cephalopods, mainly Northern species already
found in shallower waters by the United States Fish Commission, were
brought up, many of them from considerable depths. The Gasteropods
and Acephala were represented by many of the species collected by the
“Lightning” and “Porcupine,” and by the United States Fish Com-
mission.
Among the Crustacea the most characteristic types were the gigantic
Pygnogonidee, a species of Willemoesia, a couple of species of Gnatho-
phausiz, Scalpellum, and large Amphipods.
Among the Fishes a large collection was made, mainly of Macrouride,
including a few new genera, which will be described by Mr. Goode, of the
United States Fish Commission. We found cod, extending to a depth
of over 300 fathoms (off George’s Shoal). Myxine and Lophius were
brought up from 360 fathoms, as well as Sebastes norvegicus. A species
of Phycis, from a depth of 233 fathoms, was found to be electric, giving
quite a strong shock to Commander Bartlett and myself. It is a small
species, about nine inches in length, of a light ashy violet color, with dull
yellowish spots along the sides.
The absence of siliceous and other sponges in the collections made
during this summer is very striking, and although the number of speci-
mens of certain species was often very great, yet the continental faune
of the northern part of the east coast of the United States is poor when
MUSEUM OF COMPARATIVE ZOOLOGY. Lot
compared to the wealth of species found in the Caribbean Sea and Gulf
of Mexico during the former cruises of the ‘ Blake.”
Commander Bartlett did everything in his power to make up for the
absence of my assistant, and I was fortunate in again finding on board
the older officers of the “ Blake,” Messrs. Sharrer, Jacoby, Peters, and
Reynolds, whose industry, energy, and interest in the work has never
flagged, and who have now attained a proficiency in deep-sea dredging
hardly deemed possible three years ago. Lieut. Mentz and Dr. Persons
joined the ‘‘ Blake” during the winter of 1879, and Mr. Duvillard was
attached to the “ Blake” as recorder during the first part of our cruise.
During this short cruise we made no less than fifty hauls: we accom-
plished nearly as much as during the three months of the first cruise in
the Gulf of Mexico.
As the greater part of the collections made during this cruise of the
“Blake” cover the extension into deep water of the ground already in
part occupied by the United States Fish Commission, I have arranged
with Professor Baird to send the bulk of the collections made north of
Cape Hatteras, for final study, to some of the naturalists to whom the
collections of the Fish Commission have been intrusted.
During the winter of 1879-80, Commander Bartlett, while sounding
in the Western Caribbean Sea, made some twenty hauls with the trawl,
dredge, and tangles. These collections, made incidentally by the officers
of the “ Blake,” show the extension of the continental fauna of the
Eastern Caribbean to its extreme western portion. Pentacrinus was
found off Santiago de Cuba, and off Kingston, Jamaica. The deep-water
fauna was found to be the same as the deep-water fauna of the Eastern
Caribbean. |
Mr. Bartlett showed that a strong current passing over a ridge, as in
the case of the Windward Passage between Cuba and San Domingo,
Swept it entirely clean, so that but little animal life was found to live
upon it. But immediately beyond this, on the Caribbean side, the
mud and silt are deposited in great quantities and animal life becomes
plenty again. This, as I have stated above, was also our experience
during the present cruise of the “Blake,” while dredging along the so-
called axis of the Gulf Stream. .
Lieut.-Commander C. D. Sigsbee accompanied us on the “Blake,” to
Superintend in person the first trial of his collecting cylinder. It was
sent down in 30 fathoms, from 5 to 25 fathoms, with quite a fresh breeze
blowing, at about eleven in the morning, in full sunlight, —a time
when, with a smooth sea, the pelagic animals would all have been found
”
52 BULLETIN OF THE
on the surface. The cylinder was found to work most satisfactorily, and
brought up a few Calani, Hydroid Meduse, such as usually occur at
the surface. A few slight modifications were suggested by Mr. Sigsbee,
and Commander Bartlett recommended the addition of a wire-gauze trap,
to facilitate the washing out of the microscopic animals which might be
collected.
On the Ist of July the Sigsbee cylinder was tried for the second
time in Lat. 39° 59’ 16” N., Lon. 70° 18/ 30” W., in 260 fathoms of
water. The surface was carefully explored with the tow-net, to see what
pelagic animals and others might be found on the surface. There were
found Calanus, Sagitta, Annelid larvae, Hydroid Medusz, Squille em-
bryos, Salpee, and a few Radiolarians. The cylinder, filled with water
which had been carefully sifted through fine muslin, was then attached
to the dredging wire, and lowered, so as to collect the animals to be found
between 5 and 50 fathoms. The time occupied by the cylinder in passing
through that space was 28 seconds. The cylinder was then brought up, .
and the sieves and gauze trap carefully washed with water, which had also
previously been strained through fine muslin. The water was carefully
examined, and we found the very same things which had a short time be-
fore been collected at the surface with the tow-net and the scoop-net :
nothing different was collected by the cylinder. The Radiolarians (two
genera) were perhaps more numerous than at the surface. A slight breeze
having sprung up after the surface collections had been examined, the
cylinder was then sent down a second time at this same station, so adjust-
ed as to collect any animal life to be found from a depth of 50 to 100
fathoms. Not only in this experiment, but in all the subsequent ones,
the same precautions were taken in regard to straining the water which
filled the cylinder at the start, as well as that used for washing out
the sieve and the gauze trap. The messenger sent down to detach and
open the machine occupied 21 seconds in reaching the (50 fathoms) point
to which the cylinder was attached, and the cylinder then occupied 30
seconds in passing to the stop at 100 fathoms. On examining the sieves,
it was found that the more common surface things, Calanus, Sagitta, An-
nelid larvee, Hydroid Medusze, and Squillze embryos, were entirely want-
ing, and there were only two Radiolarians of the same species as those
from the upper levels found after a careful scrutiny of the water. Noth-
ing additional was brought up. The cylinder was then sent down a third
time, lowered to a depth of 100 fathoms, the messenger sent down to
open it (time occupied 45”), and the cylinder travelled from 100 to
150 fathoms (time 45”), so as to collect the animal life to be obtained
MUSEUM OF COMPARATIVE ZOOLOGY. 153
between these limits. On drawing up the cylinder and washing out the
sieve of the trap, not only did we find that the water contained nothing
different from what had been brought up by the cylinder from the
lesser depth, but it did not contain even a single Radiolarian.
On the 15th of July, in Lat. 34° 28’ 25” N., Lon. 75° 22/ 50” W.,
we tried the Sigsbee cylinder for a third time, in a depth of 1,632
‘fathoms. With the same precautions before and after using it, the cylin-
der was sent to collect first between 5 and, 50 fathoms (time 30”). The
surface was somewhat ruffled, and but little was found on the surface
beyond a few Crustacean larvae and Heteropods. The cylinder con-
tained Hydroids, fragments of Siphonophores, pelagic Algz, Crustacean
larvee, and Heteropod eggs; forms which differed from these scooped
at the surface, but were identical with the species found on previous
days at the surface under more favorable surface conditions of the sea.
Next, the cylinder was arranged to collect between 50 and 100 fathoms
(time of messenger 21” from surface to 50 fathoms, time of cylinder
40” to stopper from 50 to 100 fathoms). The water was found to con-
tain only a couple of Squillez larvee, similar to those fished up at the
surface. The third time the cylinder went down at this station it was
lowered to collect from 100 to 150 fathoms (time of messenger from
surface to 100 fathoms 45”, time of cylinder in passing from 100
to 150 fathoms 45”). The water when examined contained nothing.
No Radiolarians were found at this station, either at the surface or at
any depth to which the cylinder was sent (150 fathoms).
The above experiments appear to prove conclusively that the surface
fauna of the sea is really limited to a comparatively narrow belt in
depth, and that there is no intermediate belt, so to speak, of animal
life, between those living on the bottom, or close to it, and the surface
pelagic fauna.
The experiments of using the tow-net at great depths (of 500 and
1,000 fathoms), as was done by Mr. Murray on the “Challenger,” were
not conclusive, as I have already pointed out on a former occasion, while
the so-called deep-sea Siphonophore, taken from the sounding line by
Dr. Studer on the “Gazelle,” may have come, as I have so often observed
in the Caribbean, from any depth. I do not mean, of course, to deny
that there are deep-sea Medusz. The habit common to so many of our
Acalephs (Tima, Aiquorea, Ptychogena, etc.) of swimming near the bot-
tom is well known ; Dactylometra moves near the bottom, and Polyclonia
remains during the day turned up with the disk downwards on the mud
bottom. I only wish to call attention to the uncertain methods adopted
for ascertaining at what depth they live.
154 BULLETIN OF THE MUSEUM OF COMPARATIVE ZOOLOGY.
As far as the pelagic fauna is concerned, those who have been in the
habit of collecting surface animals know full well that the least ripple
will send them below the reach of commotion ; Miiller and Baur were
the first to adopt the use of a tow-net sunk below the surface to col-
lect pelagic animals when the water was disturbed. It seems natural
to presume, as we have found from our experiments with the Sigsbee
cylinder, that this surface fauna only sinks out of reach of the disturb-
ances of the top, and does not extend downward to any great depth.
The dependence of all the pelagic forms upon food which is most abun-
dant at the surface, or near it, would naturally keep them where they
found it in greatest quantity.
Of course, with the death and decomposition of the pelagic forms,
they sink to the bottom fast enough to form an important part of the
food supply of the deep-sea animals, as can easily be ascertained by ex-
amining the intestines of the deep-water Echinoderms. ‘The variety
and abundance of the pelagic fauna, and its importance as food for ma-
rine animals, are as yet hardly realized.
One must have sailed through miles of Salpz with the associated
Crustacean, Annelid, and Mollusk larve, the Acalephs, especially the
oceanic Siphonophores, the Pteropods and Heteropods, with the Radio-
larians, Globigerine, and Algz, to form some idea how rich a field still
remains to be explored. The variety of the pelagic fauna in the course
of the Gulf Stream is probably not surpassed by that of any other part
of the ocean.
Newrort, R. 1., August 20, 1880.
zs
No. 9. — Reports of the Results of Dredging, under the Supervision of
ALEXANDER AGASSIZ, on the Hast Coast of the United States, by
the U. S. Coast Survey Steamer “ Blake,” Commander J. R. Bart-
LETT, U. S. WV.
VAL
Description of a Gravitating Trap for obtaining Specimens of Animal Life
from Intermedial Ocean-Depths. By Linut.-Commanper C. D. SicsBes,
A eg
THE old practice of dragging for animal forms at intermedial depths
by means of a tow-net, which, during the several operations of lowering,
dragging, and hauling back remained open, was not regarded by Pro-
fessor Alexander Agassiz as affording acceptable evidence of the habitat
of such specimens as were obtained, and he frequently referred to the
subject during our association on board the “ Blake” in 1878.
In March, 1880, it having been arranged that Professor Agassiz should
make another cruise on board the “ Blake,” Commander J. R. Bartlett,
U.S. N., commanding, he asked my co-operation in devising an apparatus
to meet the rigid demands of the work in question. This resulted in
the apparatus described herein, which is presented in the precise form
used with success by the “ Blake,” although, as may readily be seen, it
is open to great improvement, especially in minor details.
The “ Challenger ” had examined intermediate depths by means of tow-
nets trailing from the dredge-rope while hauling the dredge or trawl.
In such a practice it must, have been that the depths to which the nets
were sunk depended in some degree on the amount of slack rope payed
out, and also on the strain upon the dredge-rope due to the resistance en-
countered by the dredge when dragging ; it cannot therefore be said that
strictly determinate depths were examined by that method, even assum-
ing that the nets gathered nothing while being lowered and hauled back.
It occurred to me that by using an apparatus in connection with a
line and lead, payed out vertically as in sounding, and by dragging ver-
tically, instead of horizontally as formerly, there would be at least as
much certainty with regard to depths as in the old method, and that
simple mechanical devices could be invented to satisfy the conditions of
VOL. VI. —NO. 9.
156 BULLETIN OF THE
the work. The scheme has been stated in my volume on “ Deep-Sea
Sounding and Dredging,” (p. 145, foot-note,) as follows :—
“Our plan is to trap the specimens by giving to a cylinder, covered
with gauze at the upper end and having a flap valve at the lower end,
a rapid vertical descent between any two depths, as may be desired ;
the valve during such descent to keep open, but to remain closed dur-
ing the processes of lowering and hauling back with the rope. An idea
of what it is intended to effect may be stated briefly thus :— Specimens
are to be obtained between the intermediate depths a and 6. The for-
mer being the uppermost. With the apparatus in position, there-is at a
the cylinder suspended from a friction clamp in such a way that the
weight of the cylinder and its frame keeps the valve closed ; at 6 there
is a friction buffer. Lverything being ready, a small weight or messenger
is sent down, which on striking the clamp disengages the latter and also
the cylinder, when messenger, clamp, and cylinder descend by their own
weight to 6, with the valve open during the passage. When the cylinder-
frame strikes the buffer at b, the valve is thereupon closed, and it is kept
closed thereafter by the weight of the messenger, clamp, and cylinder.
The friction buffer, which is four inches long, may be regulated on board
to give as many feet of cushioning as desired.”
The following detailed description refers to the accompanying plate.
The copper cylinder A, riveted to the wrought-iron frame B, has a
flap or clapper valve, C, opening inwards and fastened to the inner arms
of the lever D D, the latter pivoting at E. The upper end of the cylin-
der is covered with the removable wire sieve F (60 wires to the inch),
and inside the cylinder are the wire sieve G (27 wires to the inch) and
the wire funnel or trap H (27 wires to the inch).
The steel wire rope on which the cylinder travels is placed in the
loops II, at the upper and lower extremities of the frame, and is re-
tained therein by the screw-bolts J J.
The friction clamp is composed of the frame K, the two sliding chocks
L and M, the adjusting screw N, the guide screws O O, and the eccen-
tric tumbler P. :
The friction buffer is composed of the frame Q, the two sliding chocks
R and §, the adjusting screw T, the steel compression spring U, work-
ing in a chamber, and the regulating screw V. The bearing faces of the
two sliding chocks are corrugated, and the inward movement of each
chock is limited by a stud forming part of the frame and fitting loosely
within a slot in the chock. In clamping the buffer to the rope, the
chock R is always screwed in until stopped by its stud; the steel rope
MUSEUM OF COMPARATIVE ZOOLOGY. 157
is therefore always pressed between the two chocks by the elastic force
of the spring, which may be regulated as desired. To regulate the buf-
fer for any definite frictional resistance, clamp it to the rope, and move
the regulating screw V well inwards; then suspend from the buffer a
weight equal to the resistance decided upon. Move the regulating screw
outwards until the buffer slides down the rope under the influence of
the suspended weight. Since the chock R is always screwed “ home”
in clamping to the rope, the buffer remains regulated for prolonged use
with the same resistance ; and, if the latter prove satisfactory, it is
probable that the regulating screw need not be touched again for a
whole cruise, if the buffer be rinsed in lye-water each time after use.
A crank or key, W, is fitted to the squared heads of the regulating
and adjusting screws, on which it locks with a spring snap, the latter
being operated by the bent arm at one end of the crank. The stud at
the other end of the crank is for adjusting the screws J J.
The cast-iron messenger, X, is in two parts, connecting with each other
by a dovetail, — or something of similar purpose.
Professor Agassiz and Commander Bartlett added the funnel-shaped
trap, and also the leather cushion, Y, around the valve seat, after a pre-
liminary trial with the apparatus.
‘Working the Apparatus.
It is necessary to first regulate the buffer to cushion the stoppage of
the falling weights, which are, cylinder and frame 38 lbs., clamp 4 lbs.,
messenger 8 lbs., total 50lbs. The “ Blake” adopted a resistance of
about 80 lbs. (this resistance being, of course, constant during the whole
movement of the buffer), it having been found that a blow of that force
resulted in no injury to the apparatus.
On the ascent the buffer must withstand, not only the weight of the
fifty pounds of metal, but also the resistance which the water offers to
the passage through it of the several parts of the apparatus. Moreover,
when the cylinder emerges from the water, it is full of that liquid, and
with this increased weight would overcome the stated resistance of the
buffer, and force the latter downwards until the lead was reached. To
meet these conditions it was not thought advisable to increase the re-
sistance of the buffer, which would involve a heavier blow against the
apparatus, but a rope-yarn seizing or stop was placed on the rope about
fifteen or twenty feet below the buffer, beyond which the latter could
not pass.
Having secured the buffer to the rope about five or six fathoms above
158 BULLETIN OF THE MUSEUM OF COMPARATIVE ZOOLOGY.
the lead (a very heavy lead to keep the steel rope straight) and payed
out the length of rope required to span the stratum to be explored by the
cylinder, the clamp and cylinder are attached, the latter being suspended
from the former as follows. The rope having been placed between the
two sliding chocks of the clamp, the arm of the eccentric tumbler is
thrown up, which moves the chock M inwards; then, by means of the
adjusting screw, the chock L is pressed against the rope, securing the
clamp in position. The cylinder hangs four or five inches below the
clamp and is supported by a loop of soft wire which rests on the lip of
the tumbler; the ends of the wire, being rove through holes in the upper
part of the frame of the cylinder, are fastened permanently to the outer
arms of the lever to which the valve is screwed. It is seen that by this
method of suspension the weight of the cylinder and its frame is used to
keep the valve closed while paying out.* The cylinder should be filled
with water, poured down through the upper sieve, to maintain the valve
on its seat while the cylinder is being immersed. Rope is then payed
out slowly until the cylinder is at the desired depth, when the rope is
stoppered, and the messenger sent down. |
The messenger strikes the arm of the eccentric tumbler, throwing it
down and tripping the cylinder. The tumbler in falling relieves the
pressure on the sliding chock M, which is then free to recede from the
rope. Messenger, clamp, and cylinder fall together, the valve being held
open by the resistance of the water. A current is established through
the cylinder, and specimens which enter are retained by the upper sieve.
When the buffer is reached, the valve is closed by the pressure against
the outer arms of the lever.
A very slight pressure on the adjusting screw of the clamp, after the
chocks are bearing against the rope, is enough to prevent the clamp
from slipping, but by an increased pressure on the screw a greater force
is required to trip the tumbler, and by this feature the arm of the tum-
bler is utilized to break the force of the blow which the body of the
clamp receives from the falling messenger. A few rings of sheet-lead
may be laid on top of the clamp and the buffer respectively.
WasuHiIncTon, D. C., September, 1880.
* It is suggested that, in lieu of the soft wire sling, the friction clamp be constructed
to receive the end of a stiff wire rod, proceeding from the ends of the lever D D, and
that it be done in such a way that, when the valve is closed and the rod connected
with the clamp, the bottom of the latter will be in firm contact with the upper part of
the cylinder frame. Such an arrangement would effectually guard against the open-
ing of the valve with any rapidity of descent.
LM
Ze
| a S .
| SSSSSSSSSSSSS ISSSSSSSSSSSSSSSSSSSSSS SSS
eR
SSSSSSSS
SSS3
|
©
Beso SSsS Ss
|
Nye eo c-7
wx
res
2
<
AR
aly
g
®
Gravitating ‘Trap
for obtaining Animal farms
from Intermedial Oceanllepths .
Invented dy €. 2D. Sigshee Lieet. Corndr: USN,
with tm provements
s
°
y
S
>
§
&
S
t
Vv
g
8
3
&
;
&
g
s
s
>
(
ings ag
Paes
i
q
"
— es SNL —— E
ces oan ay MN Tot “
orrereraces (earemaee ee
No. 10.— On some Points in the Structure of the Embryonic Zoéa.
By WALTER FAXOoN.
TuE embryonic cuticle which clothes the larvee of the higher Crusta-
cea at the time when they leave the egg has been studied with more or
less care by Du Cane,* Spence Bate,f Fritz Miiller,t Gerbe,§ A. Dohrn,||
Stuxberg,f Claus,** and P. Mayer.tf Miiller first called attention to
the fact that the tail of this embryonic skin in certain genera of Brachy-
ura (Acheus, Maia) resembles that of the larvee of shrimps and prawns,
and working upon this hint Mayer has shown the great morphological
and phylogenetic value of a careful comparison of the caudal fin of the
embryo with that of the following free-swimming stage.
While in Mr. Agassiz’s laboratory at Newport, R. I., in the summer
of 1879, I made some observations upon the youngest larval stages of a
few Brachyura, especially Carcinus menas and Panopeus Sayi. Although
the former species is the subject of Spence Bate’s elaborate memoir on
the development of Decapod Crustacea, I am induced to publish my ob-
servations on account of the important discrepancies between them and
those of Bate.
Carcinus meenas.}{
The young of this species are peculiarly favorable for a study of the
embryonic membrane, since it is often retained for twenty-four hours
after emerging from the egg. In most species, on the contrary, the first
moult takes place within an hour or so after hatching ; indeed, in the
case of Gelasimus pugnax Smith, which I raised from the egg for the ex-
press purpose of examining the embryonic cuticle, I have only succeeded
* Ann. Nat. Hist., Vol. III. p. 488, Pl. XI. 1839.
+ Phil. Trans. Roy. Soc. London, Vol. CXLVIII. p. 589, Pl. XL. 1859.
¢ Fir Darwin, 1864. Eng. Trans. by W. S. Dallas, p. 53. 1869.
§ Comptes Rendus, Vol. LIX. p. 1102. 1864.
| Zeitschr. Wiss. Zool., Vol. XX. p. 621, Pl. XXX. 1870.
J Ofvers. Kongl. Vetensk.-Akad. Forhandl., XXX. (1873), No. 9, p. 6. 1874.
** Untersuchungen zur Erforschung der Genealogischen Grundlage des Crusta-
ceen-Systems, p. 62, Pl. X. Fig. 9. 1876.
tt Jenaische Zeitschr., Vol. XI., p. 246, Pl. XV. 1877.
tt It may not be superfluous to append a list of those who have treated of the de-
velopment of this commion and widely distributed crab : —
VOL. VI.— NO. 10.
160 BULLETIN OF THE
in obtaining it by extracting the embryo prematurely from the egg. In
this case escape from the egg and the first moult appear to take place
simultaneously.
The bursting of the egg-membranes is effected by the convulsive at-
tempts of the imprisoned embryo to extend its abdomen, which is closely
applied to the sternum within the egg. The forked tail first extricates
itself (Pl. I. Fig. 1), the antennz then protrude through the breach thus
made (Pl. I. Fig. 2), and in a very short time the contortioris of the ani-
mal have completely torn away the egg envelope. The embryo, swathed
in a delicate, perfectly transparent cuticle, now lies on the bottom of
the aquarium supinely awaiting its first moult. It is as yet incapable of
swimming about and taking food, its only movements consisting of ex-
tension and flexion of the abdomen. It is not until the veil is cast off
that the animal loses its embryonic character, and assumes the part of an
active, free-swimming larva, with mouth parts adapted for seizing prey.
On issuing from the egg, the young measures } mm. in length (Pl. I.
Fig. 3). Within the transparent cuticle the zoéa may be distinctly seen
as it will emerge on the first moult. The cuticle is not conformable to
the underlying larval integument, as it has neither dorsal nor frontal
horns, and the antenne and tail are very different. The carapace does
not at first extend far enough back to cover the base of the swimming-
feet, so that the abdomen appears much longer relatively than it does a
short time after hatching.
At the joints between the segments of the abdomen of the zoéa the
cuticle does not follow the indentations, but otherwise rests conformably
upon it. The two prongs of the forked tail of the zoéa are compressed
into a very small space by means of a complex folding produced by an
invagination of the middle third of the prongs, which does not involve
J. V. TuHompson, Phil. Trans., 1835, p. 359, Pl. V.
Henrich RATHKE, Zur Morphologie, p. 97. 1837.
C. Du Cang, Ann. Nat. Hist., Vol. III. p. 438, Pl. XI. 1839.
H. D. 8. Goopsir, Edinburgh New Phil. Jour., Vol. XXXIII. p. 181, Pl. II.
1842.
M. P. Erp, Entwicklung des Hummereies, p. 27, Pl. II. 1848.
R. Q. Coucn, “Ann. Rep. and Trans. Roy. Cornwall Polytechnic Soc. for 1843.”
(I have not seen this memoir. Some account of it is given in Bell’s History of the
British Stalk-eyed Crustacea, Introduction, pp. xlix. -liv., Figs. ¢, d, e, and pp.
79-81. 1853.)
C. Spence Bats, Phil. Trans., Vol. CXLVIII. p. 589, Pl. XL.-KLVI. 1859.
V. HeNsEN, Zeitschr. Wiss. Zool., Vol. XIII. pp. 340, 362, Pl. XX. Fig. 25.
1863. (Auditory organ of the young.)
ANTON StuxBeERG, Ofvers. Kongl. Vetensk.-Akad. Forhandl., XXX. (1873), No.
Rpt. 1874."
ee
Fe ae
MUSEUM OF COMPARATIVE ZOOLOGY. Lek
the distal third which lies within the invaginated portion like a sword
within its sheath. The same thing is seen in the spines which are found
on each border of the caudal prongs (Pl. I. Figs. 6, 7,12).* The tail of
the embryo has an entirely different form. Each half of the fork is pro-
duced into seven long spines (Pl. I. Fig. 7). Of these, the three inner
correspond to the three internal spines on the tail of the zoéa (PI. IL.
‘Fig. 2). The fourth is the homologue of the prong itself, while the fifth,
sixth, and seventh answer to the three minute ones (PI. II. Figs. 2, 5,
6, 7), which are situated on the outer side of the fork. Curiously enough,
the spines of the two stages tend to an inverse proportion, the fourth, or
smallest in the embryo, being homologous with the prong of the zoéa
tail, while the fifth, or largest, is replaced by one of the small external
spines (5’) in the subsequent stage. The fourth and seventh are naked ;
the rest are fringed with delicate hairs. In a few instances I found the
spines of the embryonic skin invaginated in the way already described
in the case of the spines of the caudal fin of the zoéa. In one example
this invagination affected the second, third, and fifth spines (counting
from the inside), (Pl. I. Fig. 6,) in another the third and fifth, in an-
other the third only. Without doubt all the longer spines are thus
invaginated within the ege.f
The two pairs of antennez of the embryo, again, have a much greater
deveiopment than in the zoéa, exceeding in length the swimming-feet,
and reaching, when stretched backwards, beyond the base of the abdo-
men (PI. I. Fig. 3). The first pair (Pl. I. Fig. 4) consists of a basal seg-
ment, within which lies the antennule of the zoéa, and which bears two
branches, viz. a long one furnished with three longitudinal rows of fine
setze, and a very short one.
The second antenne (PI. I. Fig. 5) divide a short distance from the
base into two branches, one of which has the form of a simple, blunt, fin-
ger-like process (a) ; the other divides again into three branches (1, 2, 3),
which are fringed with delicate hairs. In some specimens, at the mo-
ment of issuing from the egg, one or more of these branches is in-
folded like an inverted glove-finger. The short and blunt process (a)
encloses the spinous process (Spence Bate) of the antenna of the zcéa,
while the triple branch (+), which forms the bulk of the antenna of the
embryo, has its homologue in the external branch, or scale (squamiform
* According to Milne Edwards, the hairs of the new test of adult crabs which are
about to moult are invaginated in a similar way. (Histoire Naturelle des Crustacés,
Vol. I. p. 55. 1834.)
t Cf. Goodsir, op. cit., Pl. III. Fig. 17; Claus, op. cit., Pl. X. Fig, 9.
162 BULLETIN OF THE
appendage of Spence Bate), of the enclosed zoéa. The flagellum of the
antenna of the adult, seen in the first zoéa stage as a small protuberance
(Pl. I. Fig. 10, c), has no representative in the embryonic antenna. The
spinous process and scale of the zoéa antenna are much shortened by
invagination, like the structures of the tail already described.*
Morphology of the Antenne.—One can hardly avoid the conclusion
that, in the same way that the seven-spined forked tail of the embryo is
a reminiscence of the Gabelschwantz (P. Mayer) of the primitive Deca-
pod, so the greatly developed, setiferous antenne are an inheritance
~ from ancestors in which these appendages subserved locomotive func-
tions, as in the Vauplius. The typical second antenna of the Zoéa con-
sists of a basal stem produced at its distal end into a long serrate spine
(Pl. I. Fig. 10,a; Pl. Il. Fig. 3, i. a), and bearing besides an articulated
squamiform appendage (>). The spine is seen in a rudimentary form in
the larvee of the shrimps, prawns, and Paguride. The squamiform ap-
pendage is homologous with the external branch of the second antenna
of the larval Macroura, and with the antennal “scale” of the adult
Macroura. Both the spinous process and the squamiform appendage
become aborted in the development of the Brachyura. The flagellum of
the second pair of antennee of the adult crab is wanting in the youngest
_zoéa stages, or is represented by a small papilla merely (c).
If the relation of the embryonic antenna to the Vauplius antenna,
suggested above, be correct, it follows that the bulk of the antenna of
the Nauplius is not represented by any homologous part in the perma-
nent antenna of the crab. If, on the contrary, it be claimed that the
large fringed lobes of the embryonic antenne simply represent antennal
sete, they still point back to a primitive condition in which the first two
pairs of appendages were provided with Schwimborsten, and served as
natatory organs. .
The labrum, mandibles, metastoma, and maxille have nearly the same
form which they have in the zoéa stage which follows. The long swim-
ming-setze of the first and second maxillipeds, which play so conspicuous
-a, part in the life of the zoéa, are very much shortened by invagination,
and entirely covered by the embryonic cuticle.
The third pair of maxillipeds and the two following pairs of appendages
of the zoéa show through the transparent membrane as three pairs of
small buds (PI. I. Fig. 3, viii., ix., x.), but there are no corresponding
structures in the embryo.
* A. Dohrn, who observed similarly formed antenne in the embryo of a species of
Portunus (1. c.), has confounded the two pairs.
a alee
MUSEUM OF COMPARATIVE ZOOLOGY. 163
The young remains in this embryonic condition for about twenty-four
hours (at least in confinement). In the mean while it has increased in
size to such a degree that the delicate investing membrane is no longer
ample enough for the enclosed zoéa and the first exuviation takes place.
The cuticle of the abdomen is cast first, commonly coming off in one
piece (Pl. I. Fig. 9, 9’). The dorsal spine, which has been invaginated
like the parts already described, and laid forward over the back, begins
to be evaginated, and to erect itself, and thus aids in splitting the mem-
brane along the back. The rostrum, which has been applied to the
breast, also emerges, and the abdomen, freed from the embryonic cuti-
cle, is now used to clear the appendages of the cephalo-thorax, in this
wise : the ends of the two prongs of the tail-fork are bent so as to form
minute hooks (Pl. I. Fig. 12): when the abdomen is flexed, these little
hooks catch in the membrane covering the cephalo-thoracic appendages,
and on extending the abdomen again the membrane is torn off (Pl. IL.
Fig. 9). |
The dorsal horn is commonly evaginated, and assumes its position
with a slight backward curve even before the embryonic skin is entirely
got rid of. In specimens which have just cast the embryonic skin, a
break in the trend of the spine indicates the rim of the former invagi-
nation (Pl. I. Fig. 14). The rostral spine now projects downward at a |
right angle with the long axis of the body. The sets on the various
parts of the body unroll themselves, the mouth parts become functional
jaws, enabling the young animal to feed; the two pairs of swimming-
feet, provided each with four long swimming-sete on their external
branches, become active agents for locomotion, and now, in place of the
inert and pupa-like embryo, we have a vigorous free-swimming larva.
Besides the great difference between the two stages caused by the
sudden development of the dorsal and frontal spines, the two pairs of
antennze and the tail have an entirely different form. Both pairs of
antenne are now of relatively small size. Those of the first pair are
composed of but one segment, which carries three long sensory threads
at the tip. This segment corresponds to the basal segment of the first
antenna of the embryonic stage.
The second pair of antennz consist of a basal piece with a long ser-
rate spinous process (Pl. I. Fig. 10, a; Pl. II. Fig. 3, a), which lies in
the short, blunt process of the antenna of the embryonic stage (PI. I.
Fig. 5, a), and a short, blunt protuberance (PI. I. Fig. 10, ¢), the rudi-
ment of the antenna of the adult crab.
In addition to these processes, there is articulated to the basal piece
164 BULLETIN OF THE
a long joint with a long and a short hair on its extremity (Pl. I. Fig.
10, 6; Pl. Il. Fig. 3, b). This is the homologue of the “scale” of the
antenna in Macroura, and appears to represent the main, triple portion
of the embryonic antenna (Pl. I. Fig. 10, 6).
The tail (Pl. I. Fig. 2) has now the form so characteristic of the
zoéa of Brachyura. It is a forked piece, each prong of the fork bearing
three setze on the inner side near the base, and three minute ones on the
outer side. ‘The prongs of this forked tail themselves are homologous
with the fourth spine of the embryo tail, as before pointed out. The
outer three (5, 6, 7) diminish in size successively.
Although I succeeded in keeping some of these zoée alive for seven
days, none passed through another moult.
In Spence Bate’s classic memoir on the development of Carcinus me-
nas, the embryonic membrane which covers the zoéa when it first quits
the egg is described and figured as conformable to the whole animal,
the tail and antenne not excepted. Thus are ignored the most inter-
esting and suggestive structural features of the embryo. This error of
observation is the more remarkable, since the structures in question were
figured with approximate accuracy twenty years before by that close
observer, Captain Du Cane.*
H. D. 8. Goodsirf also seems to have seen the same structures, al-
though his description and figures are very incorrect. The “curious
brush-shaped appendages of the embryo,” which ‘drop off when the
animal has escaped from the ovum, and are replaced by spines,” { are evi-
dently the invaginated caudal spines of the embryonic cuticle, such as
are represented in our Plate I. Fig. 6. Spence Bate’s identification of
the two pairs of swimming-feet of the zoéa with the second and third
pairs of maxillipeds of the adult, instead of with the first and second
pairs, was not so strange; but why does he persist in the old error,
even in his latest papers,§ after it has been particularly pointed out by
Fritz Miiller,|| Stuxberg,{ Claus,** and others ?
* Op. cit., Pl. XI. Figs. 1, 5.
+ Edinburgh New Philosoph. Jour., Vol. XXXIII. p. 182, Pl. III. Figs. 16, 17. f
1842. |
+ Pps 382;.191,,Pli ILL Bignl7: |
§ Report on the Present State of our Knowledge of the Crustacea. Rep. Brit. i
Assoc. Adv. Sci., 1875, p. 48 ; 1876, p. 89 ; 1877, p. 44; 1878, pp. 7, 8.
| Op. cit., Eng. Trans., p. 52. ia
J Op. cit., p. 10. .
** Wiirzb. naturw. Zeitschr., 1861, p. 30. Untersuchungen zur Erforschung der
Genealogischen Grundlage des Crustaceen-Systems, p. 62. 1876.
MUSEUM OF COMPARATIVE ZOOLOGY. 165
Panopeus Sayi.
The remarkable zoéa represented on Plate II. Fig. 4, a very common
form on the southern shore of New England, I raised from the eges of
Panopeus Sayt in the summer of 1876. It differs strikingly from all
other zoée with which I am acquainted in the structure of the second
pair of antenne (1.), which consist of a single monstrously developed
spine equal in length to the rostrum. In other regards the zoéa is not
specially noteworthy. The carapace has, in addition to the rostral and
dorsal spines, a pair of short lateral spines. In the middle line of the
back, well forward toward the eyes, is a well-marked hump.
The caudal fork (Fig. 5) bears but four pairs of spines; the two exte-
rior pairs (6 and 7 in Carcinus) are wholly wanting.
To which part of the typical second antenna of the zoéa, as described
on page 162, does the long, rod-like antenna in this species correspond ?
In order to answer this question we must examine the cuticle of the
embryo. This is represented by Fig. 8 of the plate. It has a form
similar to that previously described in Carcinus menas (PI. I. Fig. 5) ;
but here the branch marked 3 is split nearly to the base, making an ap-
parently quadruple structure in place of the. triple branch of Carcinus.
The blunt, finger-like process (a) encloses the antenna of the zoéa (a’),
which is marvellously shortened by evagination. The homology of the
zoéa antenna in this case is thus fixed. It represents the spine of the
normal antenna.
The cuticle covering the first pair of antenne (Fig. 7) has the same
parts as the corresponding structure in Carcinus, and the same with the
tail (Fig. 6), in which the two external spines (6 and 7), which are en-
tirely wanting in the first stage of the zoéa, are well developed.
CAMBRIDGE, July, 1880.
166 BULLETIN OF THE MUSEUM OF COMPARATIVE ZOOLOGY.
EXPLANATION OF THE PLATES.
PLATE I. Carcinus mzenas.
Fig. 1. Embryo beginning to emerge from the egg.
Fig. 2. The same, a little further along.
Fig. 38. Embryo shortly after hatching.
Fig. 4. First antenna of the same.
Fig. 5. Second antenna of the same. The branch (3) invaginated: a/, spine
of the antenna of the zoéa seen through the cuticle ; 6/, squamiform: ap-
pendage of the antenna of the zoéa. ;
Fig. 6. ‘Tail of the same: the enclosed tail of the zoéa is shaded ; spines 2, 3, and
5 are invaginated.
7. The same : all the spines of the embryonic tail evaginated.
Fig. 8. Invaginated rostrum of the zoéa, as seen through the embryonic cuticle.
9. Young in the act of exuviating the embryonic cuticle.
Fig. 9/. The cuticle of the abdomen, just cast from Fig. 9.
Fig. 10. Second antenna of the zoéa: a, spine; b, squamiform appendage ; ¢, rudi-
ment of the flagellum of the adult. The spine and squamiform append-
age are still invaginated.
Fig. 11. To show the way the dorsal spine lies at the time of the first moult. It
has become evaginated, but not yet erected.
Fig. 12. Extremity of a prong of the caudal fork, to show the unfolding of the dis-
tal part, and the terminal hook.
Fig. 18. Rostrum and antenne of a zoéa at the moment of exuviating the embry-
onic cuticle.
Fig. 14. Dorsal spine of zoéa immediately after casting the embryo skin. The
break near the middle of the spine shows the rim of the invagination
during the earlier period.
POATE Wt:
Figs. 1-3. Carcinus mezenas.
Fig. 1. First stage of the zoéa. The appendages are marked by consecutive Roman
numerals.
Fig. 2. Tail of the same.
Fig. 38. First and second antenne of the same.
Figs. 4-10. Panopeus Sayi.
Fig. 4. First stage of the zoéa.
Fig. 5. The same, viewed from behind.
Fig. 6. Tail, with the embryonic cuticle.
Fig. 7. First antenna of the embryo.
Fig. 8. Second antenna of the embryo: a/, antenna of the zoéa seen through the
embryonic antenna.
Fig. 9. Second maxilla of embryo. The shaded part represents the appendage of
the zoéa within.
Fig. 10. End of swimming-branch of first maxilliped. The long swimming-sete are
shortened by invagination and closely invested by the embryonic cuticle.
Fig. 11. Tail of Gelasimus pugnaxz, Smith, first stage of the zoéa. Spines 5, 6, 7,
are entirely wanting. :
No. 11.—WNew Species of Selachians in the Museum Collection.
By SAMUEL GARMAN.
Scyllium ventriosum n. sp.
Bopy very stout in the anterior half, hinder portion slender. Head flattened,
as broad aslong. Snout short, blunt. Eyes medium. Spiracle small. Nostrils
near the mouth, separated by a space equal to the length of the snout, with a
valve on each side. Anterior nasal valve short, broad, more than half as wide
as the nostril, reaching the teeth ; posterior smaller, of similar shape and hidden
by the first. The distance of the valves from each other is equal to three fourths
of the length of the snout. Mouth wide, crescent-shaped. Labial folds rudi-
mentary, not visible when the mouth is closed. Teeth small, central cusp long
- and slender, with two lateral cusps on each side, the outer of which is feebly
developed, in fifty-four rows in the upper jaw. The symphysis bears no teeth;
on each side of it the first two rows are very small. Gill openings narrow, the
- fourth and fifth over the pectoral, the third twice the width of the fifth. Pec-
torals broad and short; margins convex, the anterior one fourth longer than
the posterior; angles rounded. Ventrals short, margins convex, outer ex-
_ tremity broadly curved, posterior blunted. First dorsal twice the size of the
: second, base above the posterior half of the ventral, height little less than the
length of the base, borders convex, upper extremity round, posterior blunt.
Second dorsal smaller than the anal, distant from the first the length of the
_ posterior border, its entire length less than that of the base of the anal, upper
id border curved, posterior straight, hinder angle acute. Tail less than a fourth
of the total, its width contained in its length two and a half times, notched
near the extremity on the lower side, no pit at the root. The shape of the tail
is similar to that of S. stellare or S. canicula, though broader than that of
either. Scales pedicellate, sharp and coarse. Nine circuits in the spiral of
the intestine.
Color grayish brown, spotted and banded with darker. The spots are in-
distinctly outlined, irregular in size and position. Bands transverse, twelve or
more in number ; five of them occur between the eyes and first dorsal. Lower
surface darker, olivaceous and more uniform. The specimen, an adult female,
is twenty-nine inches in length, and measures fifteen inches around the body
between dorsal and pectorals.
This species differs from S. chilense in the nasal valves, labial folds, lateral
cusps on the teeth, small second dorsal and its position with respect to the anal,
and the numerous transverse bands. One specimen from Valparaiso.
VOL. VI.—wNo. 11.
168 BULLETIN OF THE
Rhinobatus lentiginosus n. sp.
Outlines of body and fins similar to those of Horkelit and wndulatus. Ros-
tral cartilage long and narrow, a small groove near the head; ridges close
together from base to extremity. Eyes large. Spiracles half as large as the
eyes, with two folds. Head narrow, concave between the eyes. The width
of the interocular space equals that of the nostrils or their distance apart.
Half the length of the snout is less than the distance between the outer angles
of the nostrils. Mouth nearly straight, a little less than twice the width of the
head between the eyes. Scales small, smooth. Spines of the dorsal series and
the three in front of each eye very small ; those above the eye and spiracle not
noticeable. No larger spines on shoulders or rostrum. The largest spines on
the body are a group of five on the top of the end of the snout.
Color a light grayish-brown freckled with small spots of lighter ; uniform
brownish below. On the lower side of the snout there are faint indications of
markings similar to those of wndulatus.
Distinguished from Horkelit and undulatus by the colors, the horn-like
spines on the end of the snout, the absence of spines on the shoulders, the
narrowness of the head as compared with the width of the mouth, the shorter
distance from snout to mouth, and the greater distance from mouth to vent.
Total length 22.9, snout to mouth 4.1., snout to vent 9.9, and width of pectorals
7.4 inches.
An adult female secured in Florida by Prof. L. Agassiz.
Rhinobatus planiceps n. sp.
Disk, including ventrals, rhombic, about one and a half times as long as
wide. Anterior borders of pectorals straight, more than twice as long as the
convex posterior margins. Angles of pectorals rounded, the hinder not extend-
ing farther than to the vent. Outer angle of ventrals rounded, posterior acute.
Head broad, flat. Rostral cartilage medium, dilated at the extremity, with the
ridges close together in the anterior third of their length. Snout rather broad,
with rounded extremity. Eyes moderate. Spiracle immediately behind the
eye, smaller than the orbit, with a single fold on the posterior side. Anterior
nasal valve not dilated ; posterior two-lobed. Mouth nearly straight. Body
covered with shagreen above and below. Tail much depressed, with a fold on
each side. Second dorsal distant from the caudal the length of its base. Bases
of the dorsals distant from each other the length of the anterior borders.
Scales larger over the central portions of the disk. Compressed hooked spines
in a median row on back and tail, in two patches on each shoulder, and a
series above each eye. On the young these spines are much more prominent
and regular in size than on the adult.
Color brown, light between and on each side of the rostral ridges ; white
below. Young specimens with a number of small round white spots on each
side of the dorsum.
The following measurements are taken from a young male : —
MUSEUM OF COMPARATIVE ZOOLOGY. 169
Total length . . oi AW ae eT © FEO inehes:
Snout to end of ventrals Ai es sf emake a tk Pai OL
SEERERIGCHILY Fe ete ure My Sey me Oe &
Sere COMOUG SHI) Pou i be ah a oe) pee
Width of pectorals . . . .. ay! Paty Gath pe ORGS
Twenty-one specimens from Payta, Callao, eA Galapagos Islands, collected
by the Hassler Expedition.
Trigonorhina alveata n. sp.
Disk, including the ventrals, rhombic, longer than wide. Anterior borders
of pectorals nearly straight ; posterior convex. Snout truncated, as wide on
the end as the space between the eyes. Rostral cartilage wide and strong,
deeply grooved on its upper surface. Rostral ridges prominent, widely sepa-
rated, nearly or quite parallel from base to extremity. Spiracles large, equal
in diameter to the orbit, without a fold on the side. Fin angles rounded, with
the exception of the obtuse posterior angles of the dorsals. Dorsals elevated,
behind the ventrals; the length of the base of the first less than the length of
its posterior border; base of the second equal to its posterior margin. The
base of the first is equal to its distance from the ventral or the second dorsal.
Anterior nasal valves dilated, continued beyond the inner angles of the nostrils,
but separated from each other by an interspace ; posterior two-lobed. Anterior
extremities of the pectorals widely separated from the rostral cartilage, extend-
ing very little in advance of the eyes. Mouth in a low arch, regularly curved
from the corners. Teeth small, blunt, in a hundred and ten series in the upper
jaw. Claspers long, slender, knobbed at the end. Tail with a thick fold on
each side. Caudal fin rounded, without indentation. Back thickly covered
with small scales, among which are scattered larger ones. A median row of
large blunt tubercles on back and tail, and two short rows parallel to this on
each shoulder. The bases of the tubercles are so covered by the skin and small
scales that they appear as rounded prominences with a small spine on the
summit.
Color grayish brown. Near the extremities of the rostral ridges there is a
band of dark brown ; between this and another dark band which crosses the
bases of the ridges there is a light band. A dark band across the head between
the eyes is somewhat confluent with the band in front of it, which makes the
fore part of the head dark, but leaves the prominences in front of the eyes light-
colored. The remainder of the upper surface is more or less clouded by faint
indications of transverse bands. These are probably distinct in the young.
With the exception of a dark spot on the posterior angle of each pectoral, the
lower surface is white.
Total length . . . SAVE TS een ene Bagy® OP. | inches.
Snout to end of ventrals ee prce SAC tan Aa RD ONT GEG
Peto Of pectoralaity sai. a Oo 2B
SIE OCCUR ul uate Md tha ty athe"! tec oryde ROES =
Snout to mouth as) cited al aa! oa ay
Width of mouth .. ; gat) eat oy
Distance between outer angles be Hesttilas ee
170 BULLETIN OF THE
Trigonorhina exasperata.
This is the species described by Jordan and Gilbert under the name Platy-
rhina exasperata, and from which at a later date these authors drew the charac-
ters for the genus Zapteryx. The latter does not seem to differ from the genus -
Trigonorhina of Miiller and Henle. The species T. exasperata and T. alveata are
closely allied.
The genus Platyrhina is closely related to Trigonorhina, and with it belongs
to the family Rhinobatide. Both genera have broad based tubercles in a verte-
bral series and on the shoulders. Sympterygia and Platyrhina have little or no
affinity for each other. Of the Rhinobatide the latter is, perhaps, the nearest
approach to the Rajw. It is out of place with the Rajide, as located by Du-
meril and Giinther.
”
Trygon lata n. sp.
Disk quadrangular, one fourth wider than long. Anterior margins nearly
straight, forming a very blunt angle at the snout, rounded near the outer ex-
tremities ; posterior convex; inner straight a portion of their length. Ventrals
truncate, rounded. Snout produced, forming a rounded prominence in front
of the margins of the disk ; length from forehead less than the width of the
head. A line joining the wider portions of the disk passes nearer to the head
than to the shoulders. Tail more than twice as long as the body, subcylindri-
cal, without a trace of keel above, roughened with small tubercles, with an
irregular series of broad-based conical tubercles on each side; a long narrow
cutaneous expansion below has its origin opposite that of the spine, and ter-
minates in a keel which continues to the extremity. A pair of large com-
pressed erect tubercles stand immediately in front of the caudal spine, and a
single one is placed over the middle of the pelvic arch ; these suggest a con-
tinuous series in larger specimens. Three larger elongated tubercles with
points directed backward — similar to those of hastata —oceupy the middle of
the shoulder girdle. Mouth curved, six (5-6?) papillze at the bottom ; two
of these are in the middle in front where usually there is but one.
Color light olive, probably greenish in life, white below. Distinguished
from T. centrura by the prominent snout, the shape of the tubercles on the
middle of the back, and the narrowness of the posterior portion of the disk.
Length of body 16, length of tail 35.3, and width of pectorals 20.5 inches.
Collected at the Sandwich Islands by Andrew Garrett.
Trygon longa n. sp.
Disk quadrangular, about one sixth wider than long. Margins nearly
straight, anterior meeting in a blunt angle on the end of the snout. Outer
angles rounded, posterior blunt. Ventrals rounded. Tail more than twice as
long as the body, roughened with small asperities, depressed anteriorly, com-
pressed behind the spine, keeled above the compressed portion, with a long
narrow cutaneous expansion on the lower side. Mouth curved, with five
‘MUSEUM OF COMPARATIVE ZOOLOGY. 171
papille. A row of small tubercles behind the head on the shoulder girdle.
It is likely that large specimens are provided with tubercles on back and tail.
Distinguished from 7’, lata by the shape of the disk and snout, and the keel on
the tail ; from 7. centrura by the straight margins of the pectorals and the keel.
One specimen secured at Acapulco, Mexico, by Prof. Alex. Agassiz. One
light-colored, reddish-brown specimen from Panama, by the Hassler Expedi-
tion.
Length of body 11.5, length of tail 28, and width of pectorals 13.8 inches.
Length of body of second specimen 9.3, length of tail 24.5, and width of pecto-
rals 11.2 inches.
Trygon brevis n. sp.
Disk quadrangular, a little wider than long. Anterior margins nearly
straight, curved near the outer extremities to meet the convex posteriors, meet-
ing in a blunt angle on the end of the snout. Outer and posterior extremities
of pectorals round, without trace of angles. Ventrals broad, truncate, with
angles rounded. Tail less than one and a half times the length of the disk,
tapering to an acute point, depressed as far as to the spine, thence compressed
to the end of the cutaneous fold and round from this point to the end, with a
short elevated membranous expansion behind the spine, and a longer and wider
one on the lower side extending below the former and the spine. The expan-
sions have their hinder extremities opposed ; they end quite abruptly, and are
widest near the termination. Mouth with five papilla, outer small. Teeth
small, blunt. Upper jaw indented in the middle; lower, with a prominence in
front. Disk naked in the young. Adult specimens have three rows of tuber-
cles on the middle of the back disposed as are those of T. hustata. A large
specimen from Payta has three large, erect, broad-based tubercles in front of
the caudal spine, and the tail rough with smaller ones. The short rows on the
shoulders contain from one to four, and probably increase in number with age,
as is the case with closely allied species from the Atlantic coast.
Color olive or grayish brown, reddish near the edges ; below white, with
round spots of brownish under the base of the tail. .
Compared with hastata this species differs in the shorter tail, the rounder
extremities of the disk, and the shape and size of the tubercles and membra-
nous fins.
T. hastata has no expansion on the top of the tail, and that on the lower side
is very long, of moderate width, and tapers gradually. Those of brevis are
comparatively short and broad ; they rise gradually and terminate abruptly.
From T. Sayz this species is to be distinguished by the great development of
the caudal expansions, their shape and length, and by the tubercles on shoul-
ders and tail. A large female measured in length of body 17, length of tail 23,
and width of pectorals 18 inches ; a young male, length of body 8.1, length of
tail 12, width of pectorals 9.2 inches,
Including this and the preceding, the number of American species properly
belonging to the genus Trygon is increased to seven.
172 BULLETIN OF THE MUSEUM OF COMPARATIVE ZOOLOGY.
Trygon brachyurus and T. reticulatus, recently described by Dr. Giinther,
belong to the genus Potamotrygon. The species redescribed and figured by
Dr. Steindachner in 1878 as Teniura magdalene also belongs to that genus.
It needs but a slight knowledge of the anatomical differences existing between
the Potamotrygones and the Teniure proper to convince any one that both
cannot be retained in the genus Tenwura.
CAMBRIDGE, October, 1880.
BULLETIN
OF THE
MUSEUM OF COMPARATIVE ZOOLOGY
AT
HARVARD COLLEGE, IN CAMBRIDGE.
| VOL: VL.
Parr [f.—No. 12.
CAMBRIDGE, MASS., U.S. A.
1881.
UNIVERSITY PREsS:
Joun Wi son AND Son, CAMBRIDGE.
CONTENTS.
PART if.
Binney. By E. L. Mark
A. OBSERVATIONS
I. Maturation
II. Fecundation .
III. Segmentation
B. BIBLIOGRAPHY
I. Limax
1. Egg Papelaness ae
2. The Yolk and its Changes .
II. Review of Maturation, Fecundation, and Cell- Division
1. Cell-Division
@ Asters. ;
b. Quiescent Nuclei
c. The Nucleus during Division
Introductory
a, Segmentation
B. Tissues
y. Plants
2. Maturation
3. Fecundation .
C. THEORETICAL CONSIDERATIONS AND GENERAL CONCLUSIONS
Promorphology of the Ovum
Polar Phenomena
Asters .
Spiral Asters
Nuclear Spindle .
Origin of Nuclei
Germinative Vesicle
Polar Globules
APPENDIX
ALPHABETIC LisT OF THE Treen
INDEX To AUTHORS CITED IN THE TEXT
EXPLANATION OF THE FIGURES
PAGE
No. 12. — Maturation, Fecundation, and Segmentation of Limax campestris,
173
173
Uy
215
222
232
232
232
235
244
244
245
253
272
272
276
341
366
387
368
512
512
514
519
533
536
539
545
547
558
591
615
617
’ wal wif om
Leet Pa c
‘ 4 a
+5 a:
us »
ie ra P
i f etre
; woe
a i a
ALL
See
t , oh Matas:
< ie ai Pe
fi . . : me tae ‘ey ate
oo ; 2 iy P in lewwge
i 12. — Maturation, Fecundation, and Segmentation of Limax
campestris, Binney. By HE. L. Mark.*
Tue observations of the past five years ft on the earliest stages in
ontogeny have contributed more to the solid advancement of biological
knowledge, than those of any corresponding interval since the studies
of Max Schultze and others paved the way to a science of Biology.
More refined methods of research have resulted in more exact knowl-
edge of phenomena. A closer study of details has opened the way to
a broader comprehension of their significance.
It was with the hope of adding something to the empirical acquisi-
tions in this field, that I undertook the studies whose results follow.
A. OBSERVATIONS.
The eggs of Limax campestris, Binney, are found in moist places, pro-
tected from the drying influences of direct sunlight and currents of air.
They are frequently met with in the vicinity of a small stream, some
stagnant pool, or in low meadow-land. Open woodland presents favor-
able conditions for their development, affording sufficient warmth, and
preventing too direct sunlight and constant winds. In such locations
loose piles of decaying wood are often chosen for the deposit of eggs.
At other times, when the ground is less protected, they may be found
under loose stones, or even in the bed of some spring-time water chan-
nel, where crevices in clumps of earth afford protection. The most of
the material which I have studied was obtained from slugs kept in
confinement. These were collected from partially shaded ground with
Scanty grass-growth, in the vicinity of Fredonia, N. Y. A portion,
however, were from low grass-land near the Museum of Comparative
Zoblogy in Cambridge.
* I desire to acknowledge my indebtedness for the use of books to the extensive
libraries connected with the University, as well as to the Boston Society of Natural
History, the Boston Public Library, and the Boston Medical Library. I am under
obligations to the librarians of all these institutions for personal or official favors, for
which I take this opportunity of expressing my thanks.
+ The unfortunate delays which have attended the publication of this paper are
liable to mislead the reader, unless it is borne in mind that it was prepared early
in 1879. See a preliminary notice in Zool. Anzeiger, 2 Jahrg., p. 493.
VOL. VI.— No. 12.
174 BULLETIN OF THE
The eggs are usually found in clusters of about a dozen each, though
the number is subject to considerable variation. Sometimes they are
only loosely collected together, or even moderately scattered over an
area of a few inches; at others, they are closely packed in a more or
less rounded mass. Owing to the nature of the place chosen for de-
posit, they are often arranged in rows, as in the narrow cracks of moist,
decaying wood, or in the chinks in cakes of earth. On splitting the
wood or breaking open the earth, they are occasionally found to fill all
the available space completely, and if the cavity is broad and shallow
they are accordingly arranged in rows a single layer deep. It is won-
derful into what narrow crevices the eggs are sometimes crowded, ap-
parently for better protection from enemies.
They vary in external appearance according to the hygrometric con-
ditions in which they are found. If the requisite amount of moisture
is available, they are of a full, plump outline, and resemble beads of
pearl or frosted silver. If their surroundings are dry, they have a
shrivelled look, are more or less flattened, and have a faint yellowish
tint. Moisture restores them to their normal shape and color.
A careful examination will show some modifications of form, especially
if the eggs are taken from different groups. Those taken from a single
mass are usually rather uniform in appearance, though they may show
noticeable differences. The same is true of their dimensions. The
average long diameter is a little more than 2 mm. The short diam-
eter may almost equal the long diameter, or it may be hardly more
than half as long.
Sections of eggs at right angles to the long axis are almost circular,
and never differ in any constant manner from that form; but sections
coinciding with the long axis would, in most cases, show oval outlines
varying, as has been indicated, in the proportions of their axes. The
curvature at either end of this oval is usually about the same, al-
though in some cases one is more pointed than the other. Furthermore,
one end (sometimes both) may be drawn out into a sort of cue, which
varies greatly in different eggs. Rarely the cues of a couple are con-
tinuous. In those found at Fredonia I have never seen more than two
thus united. Usually all are quite separate, even though lying in
groups close together. In those found at Cambridge I have observed
a greater tendency to this union, and once counted thirty thus joined
into a delicate rosary. There could be no doubt in this case that all
were laid by the same individual, and in regular succession. Indirect
evidence that those contained in a given mass were also all laid at the
MUSEUM OF COMPARATIVE ZOOLOGY. 175
same time (i. e. in rapid succession) is usually to be found in the com-
parative uniformity in size and shape which the individual eggs of the
group present. The greatest number observed which thus indirectly
gave evidence of belonging to a single deposit was thirty-seven ; on the
other hand, it is quite certain that a very small number may be deposited
at one time by slugs that are held in confinement. That the same is
true of unconfined animals, I can only infer from finding, now and then,
small groups or single eggs far removed from any others.
The external surface of the egg is not smooth, but raised in almost
inperceptible bosses, which give to it the frosted look mentioned. Im-
mersed in water and examined under a low power of the microscope,
it is seen to be composed of a central, slightly yellowish, homogene-
ous portion, much more nearly spherical than the whole egg, and of
two thick coats of investment, which are colorless, and give it rigidity
and a great degree of elasticity. The central mass occupies from two
thirds to four fifths of the diameter of the whole egg. The two envel-
oping layers are not of uniform thickness, and may become af one or
both ends exceedingly thin., The outer layer is composed of colorless
lamine, which are for the most part nearly concentric, although at
intervals they may become thinner and disappear. The cue is formed
from this layer alone. There may often be distinguished a half-dozen
principal laminz, and also, with a higher magnifying power, secondary
laminz of varying thickness, and often in large numbers, The inner
layer is likewise colorless and transparent, but shows no trace of lamina-
tion.- When the outer layer is cut, it is found to be resistent and
elastic; but the inner layer offers less resistance and is rather viscid.
The inner layer is separated from the central, yellowish mass by a very
firm, structureless membrane, which exhibits a great tendency to wrinkle,
especially when moisture is withdrawn from theegg. This firm structure
is the membrana albuminis. The contained yellowish substance is viscid,
like the white of the hen’s egg, and like it is albuminous. In the
freshly laid egg it appears quite homogeneous. It is called the albu-
minous envelope, but from its great abundance here its nature as an
envelope is not striking. In this substance are suspended two struc-
tures which are conspicuous in all freshly laid eggs when examined with
a sufficiently high power. One of these is tortuous, and usually ex-
tends from near the surface of the albumen to the vicinity of the other
structure. It resembles an irregularly twisted, or here and there con-
stricted, thin-walled tube. As I hope to make it the object of further
study hereafter, I will only add that it has been compared to the chalaza
176 BULLETIN OF THE
of the hen’s egg, and will pass to the consideration of the other body,
— the vitellus, or egg proper, —to which all the other parts are simply
accessories. This vitellus, or yolk, has not more than one twentieth the
diameter of the whole egg, and when the latter is freshly laid it appears
as a minute speck, 125 yw. in diameter, just visible to the unaided eye
as a whitish dot, which usually has an eccentric position. It is to the
study of the yolk, and the changes it undergoes, that I shall confine my
attention.
Some of these changes may be followed in the living egg under the
microscope ; other and remarkable changes, which up to within a few
years had escaped the attention of embryologists, are meanwhile going
on within the yolk, and are either altogether hidden, or are only par-
tially visible to one studying the living specimen. It is only by the use
of certain acid reagents, which have the immediate effect of killing the
ege, and at the same time of hardening it, that these internal conditions
may be successfully studied. In considering the successive metamor-
phoses which the yolk undergoes, it will perhaps be best to follow the
course which the observer is compelled to take; that is, to notice first
what may be observed in the living egg, and then to supplement the
knowledge thus gained by such instantaneous pictures as the hardening
process affords. The more numerous these views, and the more frequent
and regular the intervals at which they are taken, the more complete
will be the data for interpreting these indirectly observed phenomena.
The changes which it is proposed to follow in this paper are only such
as occur between the time the eggs are excluded and the end of the
first segmentation. Inasmuch as the following observations begin with
the deposited egg, —i.e. do not include a study of the ovarian egg, nor
of any of the changes it undergoes within the body of the parent, —
I cannot claim for them the completeness I wish they possessed.
Recent studies on the very early stages of eggs of other animals will,
however, enable us to make a better use of these limited observations
than could be made otherwise. For the time indicated, I trust they
will be found tolerably complete and connected.
The nature of the phenomena which transpire within the limits of the
time selected ailow one to group the observations about three principal
heads : —
1. The changes connected with the ripening of the egg.
2. Fecundation of the mature egg.
3. Segmentation, or cleavage.
The observations under the first will be least complete, because they —
MUSEUM OF COMPARATIVE ZOOLOGY. 177
commence after a part of these maturation changes have already tran-
spired. These three series of events will be treated in the order men-
tioned, as that is substantially the order of their occurrence in time ;
it should be mentioned, however, that they are not strictly and com-
pletely consecutive, for each series of changes is still incomplete at the
beginning of the next following, — there is, as it were, an overlapping
in time, — and for this reason it will be less advisable to follow the strict
chronological, than the physiological order as above indicated.
As far as regards what may be observed on the living egg, the very
accurate studies of Nicholas Warneck, though made as long ago as
1850, leave very little room for additions.
It was some time after my first studies (middle April — middle May,
1877) on Limax were ended before the opportunity was afforded for an
examination of the literature on the development of pulmonates, which
was entirely inaccessible to me at the time I was making the observa-
tions. Among other references in Bronn’s Die Klassen und Ordnungen
des Thier-Reichs was that which first directed my attention to this valu-
able paper by Warneck, hitherto unknown to me even by title. I was
temporarily deterred from publishing my studies by the fact that this
observer had already published so truthful and complete an account of
the development in the case of a slug very nearly related to the one
which had formed the basis of my investigations. There were still
some points (more especially in the stages of segmentation, which will
fall outside the limits of the present paper) in which my observations
were at variance with those of the Russian naturalist. It was in part
these matters of disagreement, but more especially the influence of the
recent writings of Biitschli, Hertwig, Fol, and others, which determined
me, early in 1878, to renew my observations at the first opportunity, and
to address particular attention to the phenomena to be observed before
_ and during the first segmentation. I was able to devote only a few days
to this study in Cambridge, during the latter part of June. The most
of the observations were made at Fredonia, in August, 1878.
I. MATURATION.
In eggs examined directly after their deposit the vitellus appears
as a spherical mass of a slightly yellowish or brownish tint, with per-
fectly clear, sharp outline, about 0.125 mm. in diameter. It has greater
density than the surrounding albumen. Its opacity is occasioned by
an immense number of granulations, varying in size. Part of these
VOL. VI.— No. 12. 12
178 BULLETIN OF THE
promptly swell when, by rupture of the yolk, they are brought into
contact with water, and assume spherical contours, with delicate out-
lines and diameters varying from 2 to 8 pw. Others remain small and
of greater refractive power, under the same circumstances. They sel-
dom exceed a fraction of a micro-millimeter (4) in diameter. (Fig. 26.)
These granules are held in suspension by a viscid transparent proto-
plasm. ‘Their distribution is not always uniform, so that an irregular
cloudy appearance often characterizes the yolk. In any optical section
the peripheral portions of the sphere, owing to the diminished quantity
of these granules which the light is compelled to traverse, seem less
opaque than the central portions. A very thin shell of protoplasm
at the surface is entirely destitute of granulations, though the yolk is
certainly not provided with a distinct membrane, the so-called membrana
vitellina. Toward the centre of the sphere the opacity is not, however,
‘a constantly increasing one, for at or near this point there appears an
elongated lighter portion, which is not distinctly limited, but shades
gradually into the darker surrounding portions. This is caused by the
absence of yolk granules from the central part of the vitellus. I have
not been fortunate enough to secure an egg in which this central spot
was perfectly spherical, as did Warneck; already a lengthening had
taken place, and in most cases it appeared as two contiguous lumi-
nous areas. These become more extensive in the course of a few min-
utes, and soon appear so displaced that one is much nearer the surface
of the yolk than at first. It is only in exceptional cases that these
light spots can be seen, previous to the time when one of them appears
near the surface. The more superficial spot is then the more conspic-
uous. As these draw nearer to one side of the yolk, the granules seem
gradually to recede from that side toward which the clear bodies are
tending, so that a considerable portion of the yolk appears comparatively
transparent. After several minutes the outer spot reaches the surface,
and is less sharply marked, probably because of the increasing transpar-
ency in the surrounding substance. The deeper spot is now very near
the centre of the yolk, and only faintly indicated. After a short time
the outer spot is flattened against the surface, and gradually acquires a
greater superficial extent. There is now a slow accumulation of per-
fectly clear protoplasm at this side of the yolk; it is thickest where the
light spot first touched the surface, and thins away gradually on all
sides. This is all accomplished in about an hour after extrusion, though
liable to some variation, the changes being more rapid in proportion to
the elevation of temperature.
MUSEUM OF COMPARATIVE ZOOLOGY. 179
Up to this time the egg has remained without perceptible change of
outline. With continued increase in the extent of the cap of clear
protoplasm, which in section appears crescent-shaped, there is a slight
elongation of one axis of the yolk, which gradually becomes more notice-
able in the form of a low conical elevation at the side already indicated
as that toward which the central spots tend. For the sake of precision
I will call this the animal pole of the yolk, the opposite, the vegetative
pole.
Thus far the changes, whether within or without, have been so slow
as to be recognizable only after the lapse of some minutes; but now
‘there begins at the middle of this crescent-like thickening a more rapid
movement. The centre of this clear portion of protoplasm rises promptly
in the form of a low, rounded eminence, of limited extent, which first
becomes somewhat conical, and then assumes a more rectangular out-
line, in that its sides become nearly parallel. In this condition, it is
really a low cylinder, with one end free and rounded, the other in con-
tinuation with the vitellus. (Fig. 1.) Sometimes this elevation seems to
remain almost entirely free from opaque substance ; at other times, gran-
ules accumulate to such an extent as to make the central portion of the
protuberance appear very dark in transmitted light, and correspondingly
white when seen by reflected light. The outline of the protuberance is
sometimes slightly irregular and angular, although usually it is quite full
and rounded. Without cessation it continues to change, principally by
the mutual approximation of the sides of the cylinder at its base. This
approximation takes the form of a constriction which is at first (Fig. 2)
a broad furrow extending all around the cylinder. This furrow grad-
ually becomes narrower and deeper (Fig. 3), and the excrescence which
is thus being cut off takes a distinctly rounded form. The granulations
now often appear gathered into the distal portion of the protuberance.
Finally, the constriction deepens until there is only a slender thread of
protoplasm joining the smaller and the greater sphere. This often per-
sists for some time (Fig. 15), but finally ruptures, and sets free a small
spheroidal body, with perfectly sharp and delicate outline, which is the
first ‘polar globule.” It is only five or ten minutes from its first ap-
pearance till it has the form of a sphere attached by a slender thread.
During the formation of this first polar globule other changes are
taking place, to the consideration of which it is now necessary to return.
The elongation of the yolk in the direction of the animal radius (as I
Shall call that radius which terminates in the animal pole) is very soon
followed by its flattening in the direction of the same line. It is the
180 BULLETIN OF THE
animal rather than the vegetative pole which shows the greater degree of
flattening. This modification of the general form of the yolk reaches its
maximum as the constriction at the base of the polar cylinder begins to
deepen. But it is not alone a flattening which is noticeable at this time:
the whole contour of the yolk becomes conspicuously modified. Whereas,
at the first appearance of the protuberance, it has already become slightly
flattened, it still remains symmetrical as regards the polar axis. Very
soon, however, it becomes irregular, and more or less angular in its
outline, and often appears remarkably unsymmetrical. During these
few minutes it is constantly undergoing a slow change of form, which
seems to affect every part of the yolk, and to be accompanied by redis-
tributions of the granular substance of the vitellus, so that now one and
then another portion becomes more opaque. As the detachment of the
polar globule comes nearer to realization, these changes become less no-
ticeable,* and finally, when the act is completed, the yolk has resumed
its spherical form, and shows the same clear, even outline which had
previously characterized it for so long a time. At the close of this act,
a single, poorly defined clear spot is seen near the surface at the animal
pole. The region of this pole still retains to a considerable extent its
transparency, and a thin surface portion of clear protoplasm envelops
the yolk on all sides. It is thickest at the animal pole, and thinnest at
the vegetative. The portion immediately underlying the polar globule
sometimes presents a peculiar striate aspect, which I have been unable
fully to explain by other methods of study. The appearance is that of
fine parallel striations, sometimes having the same direction as the
animal axis (Fig. 49), sometimes oblique to it, or, on the other hand
(Fig. 27), of two systems of parallel lines crossing each other at a con-
siderable angle. These systems of striations seemed to be changing in
position, yet without any recognizable regularity. They are probably
astral rays or fibres of a nuclear spindle. (See below.) Gradually the
vitelline granulations encroach on this peripheral clear layer, and it
almost or entirely disappears.
Returning now to a consideration of the smaller sphere, it is found
that the first polar globules differ considerably in size (25 p to 40 yw), in
different eggs, even though the yolks be of uniform diameter. When
entirely detached, the polar globule is quite spherical, and remains for a
* In another species of Limax I have seen, since the above was written, very prom-
inent pseudopodal elevations of the yolk at the animal pole toward the close of the
formation of the second polar globule (Fig. 95). Compare the explanation of the
figure,
ae
MUSEUM OF COMPARATIVE ZOOLOGY. 181
short time tangent to the vitellus; but soon there appears between
the two a perceptible interspace, which continues to increase for some
minutes. The polar globule occasionally becomes removed a distance
equal to its own diameter; more frequently, it is somewhat nearer the
vitellus when this separation ceases. It often remains for some time at
a distance from the vitellus, and then the interval gradually diminishes
again. At first I was inclined to think this might be due to a slow change
in the form of the vitellus, and that the motion of the polar globule was
consequently more apparent than real; but the more I have watched it,
the less have I been able to satisfy myself that such is really the case.
About an hour after the appearance of the first polar globule, — dur-
ing which the external form of the yolk has remained without noticeable
change, the crescent-shaped accumulation of clear protoplasm has disap-
peared, and the clear spot has become obscured, and again more distinct,
—there begins again the accumulation of clear protoplasm at the ani-
mal pole, which, as before, varies much in its extent in different eggs.
(Figs. 5, 10°)
Two or three times I have noticed just at this epoch a very peculiar
behavior on the part of the first polar globule (Figs.11-13). It seemed
suddenly to give way on the side directed toward the vitellus ; and its
substance, which became as suddenly changed from almost complete
transparency to a granular and opaque condition, was rapidly projected
toward the animal pole of the yolk, with which it seemed to come in
contact. This certainly does not always occur, nor can I offer any sat-
isfactory explanation of its occasionally happening at this particular
instant, i. e. just before the first appearance of the second polar globule.
I have thought it might be due to the possibility that a change in the
form of the yolk causes the rupture of an unobserved delicate connecting
filament of protoplasm. But that does not seem very probable, inasmuch
as the distance between the vitellus and the globule is such as to allow
the discovery of such a thread of connection, if one really exist.
Occasionally there is to be seen in the yolk at this time a second clear
spot, which lies much nearer its centre than the one which has now
come to the surface and has become partially lost in the crescent of
clear protoplasm. Usually one sees nothing of this deeper spot, owing
to the abundance and opacity of the vitelline granules.
The changes which accompany the production of the second polar
globule are so nearly identical with those which mark the appearance of
the first, that attention need be called to only a few points in which
they seem to differ.
182 BULLETIN OF THE
I have noticed that very often the constriction about the base of the
second polar cylinder advanced much more rapidly from one side than
from the other, so that the axis of the cylinder, or becoming globule,
regularly assumed a direction quite oblique to that of the polar axis of
the yolk, and that (Fig. 19) consequently the point of final attachment
was uniformly at some distance from the animal pole.
The second globule is very often somewhat smaller than the first, hay-
ing three quarters or only two thirds the diameter of the latter. When
first detached the second seems to push before it the first, but at length
they assume positions alongside each other in contact with the vitellus.
I have never observed the formation of more than two polar globules,
and never, when traced under normal conditions, aless number. Neither
have I seen anything which could be compared to a division of either of
the already formed polar globules, nor yet, with the exception of a sin-
gle somewhat doubtful case, any instance in which as many as three
globules existed near a single vitellus.
I have noticed no other constant differences in the polar globules.
The interval between them and the vitellus increases after the detach-
ment of the second globule, but subsequently both come to lie much
closer to the yolk, almost always in immediate contact with it. Both
often retain a spherical form for a considerable time, during several
successive segmentations at least. In other cases, one or both exhibit
an irregular and wrinkled appearance, due most likely, in all cases, to
such a collapse and partial loss of substance as have in several instances
been directly observed. I believe that there is no regularity about
this, and that one globule is quite as likely to present this appearance
as the other, if only one is thus affected. In this collapsed condition
they continue to exist even in the most advanced stages. As is well
known, they take no part in the formation of the tissues of the em-
bryo.
We will now return to a consideration of the vitellus. Much as in
the case of the first polar globule, the changes in the form of the
yolk which accompany the production of the second are followed by
an externally quiescent state, in which the vitellus, having once more
assumed the spherical form, seems to be resting from its labors. The
crescent-like shell of clear protoplasm at the animal pole again suf
fers the vitelline granules to encroach upon its acquired territory, so
that the observer sees only a very neatly outlined sphere. It appears
whitish, or slightly yellowish, in reflected light, and more or less opaque
when viewed with transmitted light; it hangs suspended in the albu-
MUSEUM OF COMPARATIVE ZOOLOGY. 183
men like a planet, and at its side the two polar globules, of the same
exquisite outline, are poised like a pair of satellites. A careful exami-
nation, even with reflected light, shows that the halves of the sphere are
not quite alike. Notwithstanding the disappearance of the crescent as
a distinct feature, the animal half still appears more glassy and not so
white as the vegetative hemisphere, yet the one passes into the other
without any abrupt transition. In transmitted light the distinction is
even more apparent. Near this more translucent animal pole one may
sometimes see a faint circular spot (Fig. 6) of still greater clearness,
fading away gradually on all sides, but more often only a general trans-
lucency of this half of the yolk is noticeable. Even this gradually
vanishes, and there follows a period of still greater obscurity. The gran-
ulations are grouped in ill-defined shadowy masses, which one feels like
comparing to clouds, and again are re-grouped and re-distributed, ap-
parently without definite order or effect. Sometimes, however, these
changes have been observed to have considerable regularity. The most
common appearance, though this has been seen only a few times, is that
of a nearly equatorial zone (Figs. 21, 33, 36, 51) of protoplasm, from
which the vitelline granules are almost wholly eliminated. The position
of this zone varies somewhat in different eggs, and in the same egg has
been observed gradually to alter in form and extent. Soon after its
appearance, it is seen as a band of narrow surface exposure, but of great
depth, so that in optical section (Fig. 33) it extends to near the centre
of the vitellus, becoming thinner the nearer it approaches this point.
The outline thus presented in a section is that of two narrow wedges
with their bases lying in the surface of the yolk near its equator, and
their apices directed toward, and almost reaching, each other. In the
course of twenty or thirty minutes the zone has become broader (Fig. 36),
and a sectional view shows that the deeper edge, corresponding to the apex
of the wedge, has become much rounded, so that the zone is now limited
to the more superficial portion of the yolk. After twenty minutes more
have elapsed, it has become still further restricted in its centripetal ex-
tension (Fig. 34), and is rapidly becoming indistinct on account of the
encroachment of yolk granules. But these changes, as well as the less
regular fleecy appearances which are more frequently observable, are ac-
companied by no corresponding alterations in the contour of the vitellus
as a whole: the latter stills retains its simplicity of form.
Such changes as have just been traced are not the only ones going on
within the yolk at this time, although it is only in favorable cases that
one has a view of other possibly more important phenomena. The
184 BULLETIN OF THE
region of the animal pole, never losing wholly its unlikeness to the rest
of the yolk, after a time shows a faint light spot of more or less cir-
cular form. At first this spot is always poorly defined, and in many
cases remains thus as long as it continues to be visible. In other cases,
especially when it is nearer the animal pole, one may at length discover
a clear-cut delicate outline, which always remains concave toward the
centre of the spot. The latter is usually circular, but sometimes it is
oval, and sometimes it has the form of an irregular body with rounded
angles. This nuclear body continues gradually to increase in size, and
at the same time to undergo slow changes of form, which, however, have
never been seen to exceed the limits above indicated. When it has
reached the size of the smaller polar globule, or somewhat earlier, a
second like clear spot is seen lying deeper in the vitellus, and conse-
quently less clearly defined (Figs. 21, 36). These bodies at first appear
homogeneous, and less refractive than the surrounding protoplasm.
Very soon, however, a few (1—3) small highly refractive corpuscles (nu-
cleoli) may be seen in them at some distance from each other. They
change their relative positions only slightly, as though passively shifted
by the changes in the form of the nuclear body. The corpuscles in-
crease in number, but I have not observed a division in any of them.
The increase in the size of the nuclear bodies is quite gradual; they
may attain, however, (Fig. 65,) a very considerable diameter (35 y).
They are respectively, the first, the so-called egg-nucleus, or female pro-
nucleus ; the second, the male pronucleus.
The formation and growth of the female pronucleus, which occupies
from one to two hours, according to temperature, constitutes the last
series of changes which belong to this head, — the phenomena of matu-
ration, — and we may now direct our attention to the results obtained in
studying this phase of egg development by other means.
For the purpose of pursuing the phenomena transpiring within the
yolk, — which for the most part can only be traced with difficulty, or not
at all, in the living specimen,-—one may have recourse to treatment
with various reagents. Acetic acid has furnished the means to this end
in the greater part of my studies.
The condition presented by the least advanced eggs which I have
been fortunate enough to secure was such as to contribute almost noth-
ing to the solution of the question, What is the exact relation between
the germinative vesicle and the first, or maturation, spindle? The eggs
of Limax are not favorable objects for the study of this important ques-
tion, — which has of late been agitated with such a fair prospect of a
MUSEUM OF COMPARATIVE ZOOLOGY. 185
satisfactory solution, —and for this reason: the changes accompanying
the metamorphosis are certainly initiated, and probably almost always
wellnigh concluded before the egg is laid.
At any rate, 1am sure that certain of the eggs (Fig. 39) I have
treated were taken immediately after deposition. 'They were immersed
in a weak preparation of acetic acid ; and yet, as before remarked, they
were so far advanced as to afford little or no evidence toward the solu-
tion of this question. The yolk thus early subjected for several hours
to the action of weak acetic acid within the normal egg envelopes, and
then carefully freed from all enveloping substances and treated with
Beale’s carmine, shows already two well-marked stars, whose peripheries
are in -contact, the whole forming the figure recently named by Whit-
man “archiamphiaster,” to distinguish it from similar figures, known
as “‘amphiasters,” which arise later in the history of the egg.
This archiamphiaster occupies the middle of the vitelline sphere.
The two stellate figures composing it are of equal size. Each is formed
by straight radiating filaments of protoplasm, which converge from
all directions toward an imaginary centre, which they never appear to
reach.
These filaments are differentiated portions of an otherwise nearly ho-
mogeneous protoplasmic mass, which has a spherical form, and tolerably
definite, though by no means sharply marked outline. The extent of
these two spherés is marked by the encroachment of the coarse deuto-
plasmic granulations held in suspension by'the remaining protoplasm
of the yolk, and their outlines are consequently more or less definite, as
this encroachment is more or less abrupt. In no case is this so sudden
as totally to obscure the continuation of a few of the radiating lines,
for a short distance, into the more granular portion of the protoplasm.
As at their peripheral ends, so, too, at their central extremities, these
- filaments do not all terminate ata uniform distance from the mathemat-
ical centre of their respective spheres. Consequently there is a small
space immediately surrounding this imaginary point of convergence,
which, although in general of a spheroidal form, may be much less regu-
lar in outline than a circle, and is not very definitely circumscribed. In
optical section it appears as a more or less circular homogeneous “ area.”
It is only a little more deeply stained in carmine than is the surrounding
protoplasm.
While most of the filaments composing the stars, or suns, are of the
same thickness, there seem to be a few that are rather more prominent.
These latter occur at intervals of 30° to 60° throughout the suns. It is
186 BULLETIN OF THE
not always the stouter lines, however, which are traceable farthest from
the centre.
The diameter of each of these sun-like or astral spheres is about one
third that of the whole vitellus, and their centres are so situated as to
divide the diameter of the yolk into three nearly equal portions, so that |
the two astral spheres appear at first sight to be simply tangent to each
other. A more careful examination shows that this region of contact
presents important, though not prominent, modifications of structure.
All the fibres for some distance around the point of tangency are contin-
uous from one sphere to the other. The stout fibres are here compara-
tively more numerous than in the other portions of the figure, and all
are more or less curved; those farthest from the central point of con-
tact are most curved. This bipolar mass constitutes a spindle-shaped
body, having its apices at the centres of the two spheres. It is the
“ Richtungsspindel ” of German writers. I shall call it the “ maturation
spindle.” The fibres which help to form it differ so little from the radial
filaments of the suns that it is difficult at first to distinguish between the
two. There is, however, still a third peculiarity which helps to empha-
size this difference. The fibres of the spindle are slightly thickened
midway between the two poles. These thickenings form the nuclear
plate (Kernplatte) of Strasburger. From the results of recent obser-
vations made on more favorable objects by numerous European ob-
servers, there is every reason to believe that this spindle-shaped body
is the result of the direct metamorphosis of the germinative vesicle, or
at least of a part of it. A careful examination, however, of all the early
stages I have seen, has failed to show satisfactorily anything of the
germinative vesicle, which a somewhat earlier stage would probably have
disclosed.* I cannot avoid repeating the fact that, at this stage, the
spindle fibres are very inconspicuously differentiated from the radial fila-
ments. Except for much more satisfactory views at a later stage, I
confess I should have been somewhat sceptical about the existence of
such a structure distinct from the stellate figures.
It will be noticed that already the vitellus has no longer an homaxial
form, but is monaxial. The differentiated axis corresponds to that of
the maturation spindle; and its two poles are, so far as I have been
able to discover, absolutely alike (haplopolar condition). This state
* In one case (Fig. 39) I saw near the plane of the nuclear plate outside the spindle
a few irregularly shaped bodies considerably larger than the granulations surrounding
them, which may possibly have been remnants of the germinative dot, or of the mem-
brane of the germinative vesicle. If not the remains of nuclear substance, I know
of nothing with which they might be compared.
MUSEUM OF COMPARATIVE ZOOLOGY. 187
is of short duration. Ata subsequent stage it will be seen that this
monaxial haplopolar form is followed by a monaxial diplopolar. Po-
tentially, I believe, this diplopolar condition already exists. In the
present state of our ignorance as to the nature and residence of the
forces which control the phenomena connected with maturation, it is not
possible to find direct evidence of such a state at this early stage. In
the eggs of many other animals, the diplopolar condition is manifest
much earlier.*
The protoplasm of the yolk not embraced by the spindle and amphi-
aster is closely crowded with highly refractive deutoplasmic granules,
which do not exhibit any system of arrangement, save that they are uni-
formly distributed. These granules are irregular in form after the
action of acid, and they vary considerably in size. In any optical sec-
tion, the peripheral portions of the yolk appear more translucent than
the central portions, not necessarily because of less abundance or less
density of the deutoplasmic elements, but simply from the diminished
amount of yolk substance which the light has to traverse to reach the
observer's eye.
It would not be true, however, to say that the granulations extend
quite up to the surface of the egg. There is a very thin, almost
imperceptible layer of substance, free from deutoplasmic elements, which
forms the outer envelope of the yolk. This is in no way to be con-
sidered as a vitelline membrane ; however sharp the external boundary
may be, the internal portion merges so gradually into the yolk substance
as to afford not the slightest ground for assuming that it is a distinct
membrane. It is hardly necessary to add, that there is no evidence of
a double contour, and that all attempts to separate as a distinct structure
_ this outer condensed portion of the yolk are quite futile.
As will be seen from Fig. 39, the uniformity in the distribution of
the yolk granules is interrupted at irregular intervals (a). Spaces im-
mediately contiguous to the surface of the yolk appear to be quite
destitute of granules, and the corresponding portions of the surface are
often raised into transparent, boss-like protuberances. These spaces —
a dozen or more in number — are irregularly distributed over the whole
yolk. They at once become conspicuous when the egg is placed in
* Iam unable to say whether the axis of the yolk corresponding with the axis of
the maturation spindle is identical with that which becomes differentiated at the
formation of the polar globules. If so, then the migration of the spindle is only a
motion of translation along this axis ; but, on the other hand, if the spindle at any
time assumes a position oblique to the radius which passes through its centre, it is
probable that the axes are not the same.
188 BULLETIN OF THE
Beale’s carmine. One may perhaps seek an explanation of this appear-
ance in a want of uniformity in the imbibition which takes place as soon
as the egg comes in contact with the ammoniacal carmine. This view
is, moreover, strengthened by the appearance of the exposed, thickened
layer of protoplasm which envelops the yolk. For in the region of
these spots the outline becomes less dark and conspicuous, as though
a softening of the envelope had here allowed a portion of the proto-
plasm to become less dense, and therefore feebly refractive. On the
other hand, a subsequent falling in of the surface at these points —
such as might naturally be expected, from the above explanation, to
follow when the object is placed in a more dense fluid, like glycerine —
has not been observed ; on the contrary, these areas continue to be
raised conspicuously above the common level of the surface of the yolk.
The protuberances have the appearance of quite naked, protruding por-
tions of clear protoplasm. Whether they are anything more than the
result of artificial ruptures of the cortical substance of the vitellus it is
difficult to say. That they may be due to the presence of spermatozoa,
which have already penetrated the yolk, is perhaps not impossible ; but
it appears to me unlikely from the irregularity in the size and configu-
ration of the spaces, as well as from the entire absence of any regular
arrangement (stellate) of the granules in the surrounding protoplasm.
I have not discovered any specially modified central portion, nor any
difference between the spots and the immediately surrounding proto-
plasm in the facility with which staining is effected. I have not ob-
served anything of this kind in eggs of more advanced stages.
What has been said of this earliest stage is based, unfortunately, on a
limited number of specimens ; and, although my notes are unequivocal in
declaring the eggs in question to be fresh-laid, I have not been able to
entirely free my mind from the suspicion that, after all, they are much
older than I have given them credit for being. The very considerable
size of the amphiaster is perhaps in itself enough to suggest the possibility »
that they were nearly ready to effect the first cleavage, and that the
aster is, consequently, the first cleavage amphiaster.
The considerations, however, which incline me to the belief indicated
above are, in addition to the notes proving the freshness of the eggs, the
following : —
1. The almost exactly central position of the amphiaster. This, it is
true, would hardly be a safe criterion to distinguish this amphiaster from
that of a second archiamphiaster, (as we shall presently see,) but is, it
seems to me, very strong evidence that we have not to do in this case
MUSEUM OF COMPARATIVE ZOOLOGY. 189
with the amphiaster of the first cleavage nucleus; for the latter has a
conspicuously eccentric position, — it lies nearer the animal than the
vegetative pole.
2. The somewhat sharper limitations of the protoplasmic spheres
(stellate figures) than prevails at the time of the first and subsequent
segmentations. And, finally, —
3: The appearance presented by the thickened envelope of the vitellus,
which seems to possess less consistency than during the later stages, and
even at intervals to be altogether interrupted. This I take to be an
indication of want of age.
I have not been fortunate enough to secure eggs in which the matura-
tion spindle exhibits a position oblique to the radius passing through its
centre, if I except a single specimen (Fig. 53), which I am inclined to
consider as a case presenting the second rather than the first archi-
amphiaster.* (See pp. 206, 207.)
The next stage which has been observed (Fig. 45) is one in which the
first maturation spindle has a radial position, one of the stars being at or
near the centre, and the other reaching with its rays very near to the
surface of the vitellus. The peripheral extremity of the radius in which
this first spindle lies marks an important place in the topography of the
ege. From this time on it forms a cardinal point, to which one may
refer all changes of form. It is the point which we have already desig-
* The reasons for considering Fig. 53 as that of the second archiamphiaster,
instead of the first, are : —
1. The egg is one of a series of seven taken immediately after their deposition by
the slug. Four of these were at once subjected to the acid, and all show the first
polar globule in an advanced state of formation. This was submitted to acid nearly
thirty minutes later, and consequently would have had time to accomplish the elim-
ination of the first polar globule, and effect the metamorphosis which its supposed
condition implies, provided it was equally advanced with the others.
2. The appearance of the yolk at the surface near the more superficial of the two
asters. In the shallow depression of its surface and the ragged edges which it presents,
the yolk so completely resembles the appearance of the vitellus after the production
of a polar globule, that I am inclined to believe that the globule has been detached and
escaped notice.
_ 38. The smaller size of the peripheral aster. It is probable that the internal star
of the second archiamphiaster is the more direct (if not the exclusive) genetic suc-
cessor of the single star remaining at the closing phases of the detachment of the first
polar globule, and therefore may be expected to be somewhat more conspicuous than
its more recently formed companion.
This last argument would have no weight if the second amphiaster arises, like the
first, from the metamorphosis of a typical nucleus, since then both stars would be of
equal age. (Comp. p. 206.)
190 BULLETIN OF THE
nated as the anzmal pole. It is often spoken of as the formative pole,
in distinction from the opposite and often less active nutritive pole.
In this condition, then, the egg manifests a diplopolar state, which
may — doubtless must — have had a potential existence before ; a state
which is now most emphatically expressed by its internal structure,
and which seems never to forsake it altogether. Whether, however,
this monaxial state be identical with that which one observes in the
earlier condition of the egg (Fig. 39) must be left undetermined for
the present. |
In this stage the maturation figure (i.e. the whole internal figure)
presents itself as a compound structure, composed of the spindle and
two nearly spherical masses of protoplasm, having the ends of the
spindle as centres, and traversed by fibres radiating from them, — in
short, the two asters of the so-called archiamphiaster.
The length of the spindle is a little more than one third the diameter
of the vitellus, and its greatest thickness is somewhat less than half its
length. Its outline, when viewed en face, is evenly curved, tapering from
its greatest thickness at the equator toward either pole, where it is lost
in the rays near the centre of the aster. The spindle embraces a large
number of fibres, — probably not less than thirty or forty, — continuous
from pole to pole. These fibres are considerably more conspicuous than
the radiating lines of the asters. The intervening substance of the
spindle appears structureless, and much less refractive than the sub-
stance of the fibres. Some of the latter exhibit, in the equatorial plane
of the spindle, thickenings of considerable size.
It does not seem that all the fibres present such thickenings ; nor, on
the other hand, am I quite certain but that some of these apparent
thickenings are really unconnected with any fibres, —at least their
irregular distribution has suggested the possibility of their being de-
tached, without having afforded as yet a sufliciently satisfactory demon-
stration of the existence of such independent granules. A view along
the axis of the spindle (Fig. 46), while it affords pretty satisfactory
evidence as to the relative position of the thickenings in the equatorial —
plane, does not prove sufficient to settle the question, for the reason
that the fibres are so minute as to be almost entirely obscured by the
overlying star. In the view thus had, one finds the number of thick-
enings to be about twenty, and that they are not distributed with any
very clearly defined order. In a later stage, however, we shall find that
the number is considerably greater, and that they are more conspicu-
ously subject to a definite plan of arrangement.
oe
MUSEUM OF COMPARATIVE ZOOLOGY. 191
The two stars, or, more exactly, spheres, of the first maturation
figure already present a difference which is not diminished as the de-
velopment of the egg advances. Not alone that there is a noticeable
difference in the magnitude of the two stars, constantly somewhat to the
disadvantage of the peripheral one, but, further, there is a sharpness to
the limitation of the outer star which is missed in the outline of the
central figure. Nor is this attributable solely to the obscuration pro-
duced by the rays of light from the deeper star having to traverse a
greater mass of granular vitelline substance than do those from the more
superficial figure. No doubt that fact enhances the difference, but the
primary cause seems to lie in the more complete exclusion of the granu-
lar elements of the vitellus from the superficial than from the deeper
sphere. In another point, too, these two stars may differ: the rays of
the outer star, instead of presenting that rectilinear appearance which
characterizes those of the deeper star, appear uniformly curved in a like
direction (Fig. 47) when the star is viewed from the animal pole. This
spiral arrangement of the radiating fibres of one or the other of the am-
phiastral stars is a phenomenon of not uncommon occurrence, and will
demand a more extended consideration a little further on. It is a less
constant feature of the outer star than the peculiarities previously
described. Aside from these differences, there seems to be no noticeable
distinction between the two asters or their relations to the portions of
the spindle so closely connected with each. There is, however, one
feature which very soon makes its appearance, or may perhaps be already
detected in a faint degree, — I mean a modification of the form of the
superficial sphere, which is accomplished at the expense of the diameter
which coincides with the polar diameter of the yolk. To be more exact,
however, this flattening in the direction of the animal radius is most
conspicuous, if not exclusively apparent, on the outer hemisphere of the
superficial aster. It is a modification which increases with the motion
of translation which the whole internal figure is destined to undergo
along this animal radius; it is perhaps only one of the physical effects
resulting from the motion.
When this maturation figure is spoken of as though it were something
by itself, it is not to be understood that it is a sharply defined object
with definite boundaries separating it from the remaining portions of the
yolk, but, on the contrary, it should be distinctly stated that at this stage
the transition from the maturation figure, on the one hand, to the en-
veloping portions of the vitellus, on the other, is quite gradual.
The latter is characterized by the deutoplasmic elements, which are
192 BULLETIN OF THE
evenly distributed through its mass, save where they come within the
reach of the influence which determines the differentiation of the sub-
stance of the maturation figure into less refractive and more refrac-
tive fibrous portions having a definite arrangement. Here these coarse
deutoplasmic elements are made to assume a corresponding radial rela-
tion. ‘They decrease in abundance toward the centres of the stellate
figures.
The figure of the whole vitellus is that of a sphere, which may already
be slightly flattened in the direction of the only differentiated axis.*
The portions which are most deeply stained in carmine are, first, the
equatorial thickenings of the spindle, and after them the central
portions of the two asters. The gradual increase from periphery to
centre in the density of each aster makes it more and more difficult, as
one approaches the centre of the star, to distinguish the compact proto-
plasmic rays from the protoplasm in which they are imbedded. For
this reason the “area” is not always at this time a region definitely
circumscribed by the central terminations of the radial fibres.
In the stage just reviewed we have seen the first archiamphiaster
fully formed, and already advanced to a position such that a continua-
tion in its motion of translation will necessarily make itself at once
apparent in the general outline of the yolk. Such a modification is, in
fact, the thing which, in the next stage (Figs. 43, 48), most forcibly
attracts attention, — not, however, in the manner one might have antici-
pated. ‘The whole vitellus becomes conspicuously flattened in the direc-
tion of its polar diameter, and at the same time presents at the animal
pole, as a sort of compensating change, a slight elevation. The latter
becomes prominent in proportion as the vitellus, as a whole, undergoes
further depression at this pole of the egg. It is as though the vitellus
at the animal pole were to sink gradually away, leaving the peripheral
end of the archiamphiaster protruding beyond the general outline. The
latter, as seen from either pole of the main axis, remains that of a circle,
or at least presents only very slight and inconstant deviations from that
form ; but the outline, as seen in profile, becomes altered, not simply,
as it would seem, by the protrusion of the maturation figure, but by a
concomitant flattening of the adjacent portions of the vitellus. The
relation of these two acts to each other and to their cause will be con-
sidered hereafter. The resulting outline is like that produced by the
insertion of the arc of a smaller circle into that of a greater one. The
* For the peculiar appearance of the outline at the animal pole of the vitellus in
Fig. 45, see the explanation of the figures.
MUSEUM OF COMPARATIVE ZOOLOGY. 193
inserted are corresponds to a circle having approximately the diameter
of the outer stellate sphere. The resistance offered by the yolk en-
velope is, however, so considerable as to cause a decided flattening of
the external half of the peripheral stellar sphere. It also results from
this resistance that the outer ends of the radiate filaments of the outer
star are curved away from the polar axis, and finally bent backward, —
much as the hairs of a soft brush would be when gently forced against
the concave surface of a highly curved watch-crystal. The effect of this
curvature in the filaments is at first quite deceptive ; for it unmistak-
ably suggests to the observer that from the apex of the protuberance
there is a funnel-shaped depression extending to near the centre of the
radiate figure, — a depression in form something like that of the corolla
of a morning-glory. This illusion is further heightened in specimens
which have been stained, by the fact that this apparently invaginated
portion is only slightly tinged in comparison with other portions of
the stellate figure, or the yolk (Fig. 43). It is, however, very certain
that no such depression actually exists, as one may be convinced by care-
fully rotating the egg and focusing the instrument so that the centres
of both stellate figures are seen distinctly at the same time. The axis
of the spindle then lies in a plane parallel with that of the microscope
stage, and its whole length is exactly in focus. If there were such a
depression at the surface which lies in the continuation of the spindle
axis, it should be observable in the outline of the yolk ; but, on the
contrary, the very transparent portion of the peripheral star shows a
sharply defined outline, convex externally, and continuous at each end
with the outline of the rest of the yolk (Figs. 43, 48).
When the egg has been subjected to the action of acetic acid, the
very fulness of the outline at the animal pole, as contrasted with the
more or less shrivelled and irregular outline of the rest of the vitellus,
is to me an indication of the high state of mechanical tension to which
this portion of the surface is subjected.
At this time the superficial portion of the protuberance seems to be-
come differentiated into a thin membrane with double contour, which is
continuous at the margin of the elevation with the less conspicuously
differentiated outer layer of the rest of the vitellus. This membrane is
at first of uniform thickness over the whole surface of the protuberance.
It is only in a subsequent stage that it assumes a different and peculiar
appearance.
As already indicated, the radiating fibres of the peripheral aster suf-
fer a bending back, which changes their original direction more or less,
VOL. VI. — No. 12. 13 :
194 BULLETIN OF THE
according as they would naturally lie near to, or more remote from, the
continuation of the spindle axis. The course of some of the fibres of
even the deeper half of this star is thus affected. The result is a
gradual diminution in the number of fibres in the outer half of the
aster, and their greater concentration near the equator of the astral
sphere. It is this increase in the number of the fibres near the equa-
tor of the aster, together with their arched course, which causes
the peculiar funnel-shaped phenomenon already described. Such sim-
ple, and yet unique, modifications of the star are not the only ones
to be found. While I believe the backward deflection of the fibres
is an invariable, a mechanically necessary feature of this stage of the
egg phenomena, I am not able to say as much of some other modi-
fications ; in fact, Iam almost certain that the latter are to be found
only occasionally. ‘They may not, perhaps, on that account, prove less
interesting. I refer to the very peculiar appearance sometimes pre-
sented by the outer aster, when one looks directly down upon the animal
pole of the egg. Instead of seeing the fibres radiate in straight lines,
as one might naturally expect and would find in the majority of cases,
it will often be discovered that they are uniformly bent into a spiral, pre-
senting thus a figure not unlike that of a turbine water-wheel (Fig. 56).
The curvature in the cases I have seen (remembering that the observer
is looking upon the animal pole) is such as would be produced by the
peripheral ends of the fibres being moved in the direction in which the
hands of a clock advance, while the centre remained fixed, or by an
opposite rotating motion of the axis of the spindle when the peripheral
ends were immovable.
This spiral phenomenon has been observed even before the aster had
“caused any elevation of the surface (Fig. 47), but not before it had
reached the periphery of the yolk. No phenomena corresponding either
to flattening, backward deflection, or spiral arrangement of the fibres,
have been observed in the deeper star up to this stage.
During the stage now under consideration the centre of the peripheral
sphere becomes conspicuously modified. It is at length occupied by a
circular, highly refractive homogeneous body, flattened in the direction
of the axis of the spindle so that it appears oval in a profile view.
This body, at times irregular in outline, appears to be surrounded by
a clear zone of uniform thickness. The appearance may be due solely
to reflection from the body itself. (Comp. Flemming, "78, p. 310.*)
* The numbers immediately following an author’s name serve the double purpose of
referring the reader to the list (p. 591) where the titles of papers are given, and of in-
forming him at once of the approximate date of: the paper in question.
MUSEUM OF COMPARATIVE ZOOLOGY. 195
The uniform thickness of the zone would favor this interpretation ; on
the other hand, it is sometimes too broad readily to admit that expla-
nation.
This body is the centre of the peripheral radiation, and corresponds
consequently to the centre of the deeper stellate figure. In the
latter, however, I have not usually succeeded in finding any correspond-
ing well-defined structure. As in the earlier stages, one sees only
an irregular area, often homogeneous, but at times apparently made
up of a small number of coalescing, not highly refractive globules.
(Comp. Fig. 55.) In only one case (Fig. 48) have I seen anything like a
sharply limited body in the centre of the deeper aster. In this case it
was of about the same size as the peripheral body, and like it appeared
slightly flattened in the direction of the spindle axis. Still, the outline
was less sharp, and the flattening less conspicuous.
The impossibility of fixing with accuracy the absolute, or even rela-
tive, degree of advancement of different eggs at this period, deprives
the observations in great measure of the value they might other-
wise have. This would be especially perplexing were it not that one
is at liberty, when the evidence is so uniform, as it fortunately is in
this case, to use the observations of others, even though made on differ-
ent animals. Not that there is no direct evidence of which to make
ase, but simply that it is less complete than it would have been, had
the eggs been more transparent.
The spindle at this stage is not always prominent. In some cases
(Fig. 43) it is with great difficulty that its fibres can be distinguished
from the radiate filaments. At other times, when the superficial pro-
tuberance and the central body of the aster are already differentiated,
its limits are very well marked.
Thickenings in its fibres are often not easily made out. Even where
there is a prominent elevation of the yolk and a sharply marked body in
the outer aster, the central zone of the spindle sometimes appears as
hardly more than a continuation of the granular protoplasm which, in
optical section, seems wedged in between the surfaces of the stellate
spheres (Fig. 43). On the other hand, eggs in which the elevation
is less pronounced (Fig. 48) may present a clearly marked median zone
of thickenings, or even two closely approximated zones. Figs. 43, 48,
(and others not reproduced on the plates,) evidently exhibit slightly
different stages, although the eggs were deposited in one bunch, cer-
tainly not more than a few seconds apart, and were subjected to the
same treatment. The prominence of the stellar elevation, which might
196 BULLETIN OF THE
at first appear to be a fair index to the advancement of the individual
eggs, seems to be of secondary importance ; for in this series the one
(Fig. 48) presenting the least elevation is the one which, to conclude
from the appearance of a subsequent stage, as well as from analogy
with observations on the eggs of other animals, is in reality the most
advanced. The evidence is found in the fact that there are two zones
of thickenings here, while in the others only one zone is discernible.
It has been clearly shown, by direct observation of living cells of both
animals and plants, that this double zone arises by the splitting into
halves of the single median zone ; and that such is really the case here
cannot be doubted, as we shall see when we come to the investigation
of the next stage. Moreover, a careful examination of the figures shows
that the centre of the outer star is nearer the surface (whither it was
certainly tending) in the eggs which, for reasons just given, we must
conclude are the more advanced.
The spindle, as in the preceding stage, is usually very stout, its thick-
ness at the equator being nearly half its length, which still remains
about one third the diameter of the vitellus.
The arrangement of the granulations in the vitellus differs but little
from that which prevailed in the last stage. There still exists a uniform
distribution of these elements save where the archiamphiaster has
caused their more or less extensive disappearance. Corresponding to
the changed position of the archiamphiaster, the area of distribution is
somewhat modified ; but otherwise I can discover no alteration in eggs
subjected to hardening processes.
The further transfer of the archiamphiaster toward the surface of the
vitellus is accompanied with continued changes, which affect its shape
more than the general form of the vitellus. Instead of pushing be-
fore it the thin covering formed at the animal pole, and emerging
from the surface as a complete spherical aster, the exposed half of the
outer star suffers a further and marked change of form, as well as re-
duction of size (Fig. 50). The centre of this stellate figure now lies
close to the surface of the vitellus, a thing which could only occur by a
displacement in the more exposed radiate fibres. What the nature
of that displacement is, can be inferred from what was seen in the last.
stage, where a mechanical deflection was so apparent.
From the position of the centre of the outer star, it follows that
the latter is now much less than a complete sphere; it is even much
less than a hemisphere. The radial extent of the portion which re-
mains is, however, about the same as before, that is to say, the radiating
MUSEUM OF COMPARATIVE ZOOLOGY. 197
fibres are of nearly the same length. Consequently the inner limita-
tion of this outer aster—the surface which abuts upon the granular
vitellus — is, as before, of nearly circular outline; the free or exposed
portion, on the other hand, has not quite the form of the are of a circle,
for the curvature is sharpest at a point directly over the centre of radia-
tion, The course of the adjacent rays is nearly parallel with this outline.
The whole figure of the outer star is thus changed from a sphere to a
form more resembling a biconvex lens, va its more highly curved
surface directed outward.
The compact body which in the earlier stages existed at the centre of
radiation still persists, although its form is further modified by a con-
tinued flattening. It is in the profile view that this body is most con-
spicuous. It corresponds, I believe, with that which Robin (’75, p. 34)
calls in Nephelis “‘un espace clair circulaire, superficiel,” but which has
been better seen and more clearly depicted by Whitman (’78%, p. 18,
and Figs. 62, 63, C. P.), in the case of Clepsine. I shall have occa-
sion to recur to this subsequently.
The modifications which the external aster has undergone, caused in
part at least by its relation to the outer envelope of the vitellus, do
not find their counterpart in a like modification of the deeper aster.
A certain amount of change may also be observed here. This aster
has also approached the animal pole; it has moved to a position at
some distance from the centre of the vitellus; there is also a slight
change in the extent of the radiate influence of which it is the expres-
sion, for the rays which reach out into the vegetative hemisphere are
somewhat longer than those belonging to the opposite half of the yolk.
Its peripheral limitation continues to be less sharply marked than that
of the outer star. The inner ends of the rays, on the other hand,
terminate at a nearly uniform distance from the centre of radiation.
The spindle itself still retains the robust proportions characteristic of
the earlier stages. Its length has not suffered appreciable change, and
its outline is less modified at the equator than in the earlier stages,
when the bending at this place often appeared quite abrupt. The inter-
stellate fibres are more distinct than formerly, and the centres of the
stars continue to be the points of convergence for the two extrem-
ities of the spindle fibres. The thickenings of the latter are more or
less widely separated, and appear as two distinct and conspicuous
zones at equal distances from the equator. When seen lengthwise of
the spindle, the numerous (40 to 50) thickenings appear arranged —
more distinctly than in the previous stage—in the form of a ring,
198 BULLETIN OF THE
neither border of which is sharply marked. Between the two zones of
thickenings are stretched delicate nearly parallel threads, which I shall
designate as ¢nterzonal filaments.
The granular elements of the yolk are distributed with the same
uniformity as before, and are only so far modified in their arrange-
ment as might have been anticipated from the changes in form, posi-
tion, and extent of the archiamphiaster. The vitellus has again as-
sumed more nearly the circular outline, aside from the protuberance
caused by the archiamphiaster. That portion of the profile where this
conical protuberance joins the sphere presents a very slight reverse
curvature. In hardened eggs the contour of the low cone is constantly
distinguishable from that of the remaining vitellus by a fulness and
evenness which are quite as noticeable as in the preceding stages. This
is the more conspicuous in some specimens from a thickening in the
envelope of the vitellus at this pole. In extreme cases (Fig. 50) the
thickness of this structure (vm?) may reach 3.5 at the pole itself,
but it thins out rapidly, so that where the base of the conical elevation
joins the vitelline sphere it is quite indistinguishable. It is sharply
marked from the underlying stellate figure, and presents in glycerine a
clear, even, though not prominent, external outline. Its substance is
finely punctate, a thing which causes me to question the interpretation
(vitelline membrane) which I was at first inclined to give this structure.
In some cases, apparently in this stage of advancement, it is represented
by only a thin homogeneous cortical layer such as is depicted in the
preceding stage (Fig. 43).*
The changes following upon the conditions last described lead directly
to the production of a small, more or less spherical body at the animal
* J am in no way prepared to insist upon the identity of these two structures.
As regards the origin of that which is to be seen in Fig. 43, I have no hesitancy in re-
ferring it to a cortical portion of the yolk itself. The structure exhibited in Fig. 50
presents peculiarities not easily harmonized with a like explanation of its origin.
Foremost is the fact of its low refracting power; secondly, its finely granular struc-
ture; and, finally, its very unequal thickness within narrow superficial limits.
Whether it may not be a comparatively thin fluid exudation from the animal
pole of the yolk coagulated by the acid, or whether it may not owe its origin to the
albumen surrounding this region of the vitellus, are possibilities which I have not
been able definitely to accept or reject. If in any way dependent on the albumen for
its origin, it is difficult to understand what should induce it to take this very peculiar
form, and why it has so sharp and even an exterior. I can recall nothing in the
development of other animals with which it may possibly be compared, unless
perhaps with the exudation from the eggs of Batrachia, described by Bambeke and
O. Hertwig.
MUSEUM OF COMPARATIVE ZOOLOGY. 199
pole, —the so-called polar globule. The steps in its formation have
already been followed in the living egg, in so far, at least, as concerns
the successive phases of its changing outline.
The slight annular depression marking the limit of the external aster
in the previous stage gradually deepens, and the transparent fibrous
protoplasm of the outer star, together with a portion of the more
granular protoplasm in its immediate vicinity, is pinched off by this
deepening constriction.
The internal alterations accompanying this process (Figs. 40-42)
are in a measure only the continuation of those noticed in the last stage.
The maturation figure has migrated farther from its central position.
The external star has undergone a more thorough metamorphosis than
the deeper one. ‘The spindle has suffered a constriction at its equator,
but its length remains nearly unaltered.
What is left of the radial structure of the outer star is discoverable
within the polar globule. A few faint lines, lying mostly near its sur-
face, are all that can now be seen; even these are not uniformly observ-
able. When present, they are often so closely applied to the surface of
the polar globule as to leave the observer for a time in doubt if he has
not before him a series of striations or foldings in the envelope of the
globule. The slightly serrated outline of that portion of the globule
which in Fig. 41 faces the vitellus, seems at first to strengthen the lat-
ter opinion ; but a careful inspection seldom fails to show that the mark-
ings are not all parallel, — that different systems cross at a slight angle,
which could hardly be expected of surface foldings. The greater part
of the contents of the polar globule show not the least.trace of such
a structure, but are simply either quite transparent and homogeneous,
or show a very fine punctate appearance, in which a few larger granules
are occasionally found. The structure of the central portion will receive
attention a little further on. The body which formed the centre of
radiation is usually no longer distinguishable, its substance possibly hav-
ing become disseminated in the globule. Occasionally, however, (comp.
Fig. 63,) one discovers, attached to the free pole of the globule and pro-
jecting inward, a prominent thickening (aa’?) which I am inclined to
consider as at least a portion of this refractive corpuscle which has by
this time gained an intimate connection with the envelope of the globule.
The deeper star, having moved further from the centre of the yolk, as
already indicated, is now tangent to the inner surface of the vitelline
Sphere. The amount of substance that is brought directly within the
influence of this star is slightly increased, principally on the side opposite
200 BULLETIN OF THE
the polar globule. It should be remarked, however, that the extent of
this influence, as evinced in the radiate structure, is subject to consider-
able variations in different eges at the same stage of development.
While a homogeneous area at the centre of this star is marked off at
times with great distinctness (Figs. 22, 25), in other cases the central
portion is less prominent. It may continue to present the appearance
previously noticed, as though originating from a few irregular and poorly
defined masses of nearly homogeneous substance. One side of this cen-
tral area is marked in a conspicuous manner, as will be seen presently,
when the structure of the spindle is considered.
The latter has now become very much modified, and, by the advance
of the constriction, is made to assume successively different forms, until
at length it is like two spindles placed end to end rather than a single
structure. What we may call the outer spindle, i. e. the outer half of
the original body, which now occupies the polar globule, is less spindle-
shaped than the inner half. I have never been fortunate enough to see
its fibres converge beyond the zone of thickenings, after the constriction
has made its appearance at the base of the polar globule. A slight con-
vergence of the interzonal filaments toward a point on the distal surface
of the globule is, however, often observable (Figs. 22, 63). After fur-
ther constriction the region of thickenings appears more expanded, as in
Fig. 25.
The internal half often preserves for some time a fusiform appear-
ance, though the theoretical apex at the centre of the stellate figure
has no visible connection with its fibres. It is only the trend of the
latter which indicates this point as coincident with the centre of the
star. The place of interruption in the fibres is dependent on the size
of the central area.
Already at the beginning of the constriction the two lateral zones (or
nuclear plates) had migrated, the one to near the border of the deeper
“area,” the other to a corresponding position relative to the refractive
body of the outer star. During the constriction the thickenings of the
former are found grouped together at the periphery of this “area,”
in such a way as to form a circular disk rather than a ring such as
was observed in the earlier stages. The outer of these migrating
zones, on the other hand, has not diminished in circumference, but
.has spread out, and still presents the annular rather than the disk-
like arrangement. When seen from the animal pole the spindle
thickenings in the polar globule (Fig. 42) consequently appear as an
ill-defined ring.
MUSEUM OF COMPARATIVE ZOOLOGY. 201
That portion of the interzonal filaments which falls within the polar
globule is gradually drawn into the thickenings; at least the fila-
ments as such disappear. That portion which remains within the
vitellus, after suffering a diminution in thickness, probably disappears
altogether; so that shortly after the separation of the first polar globule
there is found in the vitellus only a single stellate figure near the ani-
mal pole. In the polar globule, on the other hand, there is no radiate
structure, — simply a group of prominent granules which are conspic-
uous from the readiness with which they are stained in carmine.
The globule often gives evidence of being limited by a special
membrane, which must have come from the envelope which we have
traced in its origin as a covering to the rising cone of the animal pole.
As that envelope was often thick at the apex .and rapidly grew
thinner toward the base of the cone, so we find that the correspond-
ing structure is often much thickened at the distal extremity of the
globule (Fig. 22),—the point corresponding to the apex of the cone.
This thickened portion passes gradually into the envelope of the
sides and proximal face, which seldom shows more than a single contour
line. Before the complete detachment of the globule, there is formed
(Fig. 63), in the pedicel which still establishes a connection with the yolk,
at a point corresponding more or less closely with the equator of the
spindle, another thickening, which may be the equivalent of the cell-
plate (Zellplatte) of Strasburger. It is a disk of considerable thickness,
which extends quite across the pedicel, and is highly refractive. Though
not directly observed, it is reasonable to suppose that the final separa-
tion is along this disk, most likely by its division into two plates.
The events which immediately follow the formation of the first polar
globule seem to me to have been less clearly treated by those who have
engaged in the study of the phenomena than any other portion of these
remarkable changes. Nor can I add much to their elucidation ; for it is
only after carefully comparing the results of my summer’s work that I
am inclined to believe that there remains just here something of
a gap in the continuity of the best observations. It has been cus-
tomary for the second archiamphiaster to receive only a hasty de-
scription. Its origin has often been quite neglected. Because the result
in the case of both maturation spindles is the production of a polar
globule, the phenomena in the second case seem to have been considered
of only secondary value in the search for what is new. At the beginning
of this second stage careful attention is demanded to answer the ques-
tion, How does the second archiamphiaster arise 2
202 BULLETIN OF THE
Does the spindle completely disappear? Or does the vitelline half
persist ? And if it remains, does its outer end become the centre of
a new force, acting on the surrounding protoplasm to induce a new pe-
ripheral star? Or, if it vanishes, does the single star develop an-
tagonistic poles which move apart, each taking with it the half of the
great star left in the vitellus ?
So far as one can judge from the observations that have hitherto ap-
peared, the most nearly complete second archiamphiaster yet seen is one
having a spherical central aster joined by a spindle to a very incomplete
peripheral aster, whose centre of radiation lies in the surface of the
vitellus. The latter in its greatest extension is less than the half of a
complete star. That there have been important omissions from the
history of the second archiamphiaster will at once be inferred upon
consulting Fig. 23. The first polar globule has already been formed, but
still remains loosely attached to the vitellus, and further held in place
by fragmentary portions of the surrounding albumen of the egg (a).:
The second archiamphiaster is completely formed. Its axis coincides
almost exactly with the polar axis of the yolk. It lies wholly within
the vitellus, being nowhere tangent to its surface. The nearest point
of approach to the surface is immediately under the polar globule. The
composition of this second archaic figure is deserving of close attention.
The two stellate figures which make up the most of its substance are
joined by a spindle which is not very distinctly outlined.
Perhaps the most noticeable feature of the whole figure is the un-
likeness of the two stars; such a difference as we have already seen
(Fig. 45) in the first archiamphiaster. The outline of the deeper sphere
is by no means sharp, for prominent rays here and there extend into the
coarsely granular protoplasm for some distance beyond the majority of
the radiate fibres. In the case of the more superficial sphere, on the
other hand, the rays terminate at such a uniform distance from its cen-
tre that the outline is quite even, and almost circular, in whatever posi-
tion it be viewed. Otherwise the two asters are much alike: the rays
are straight in both, though more uniformly distinct in the outer than
in the deeper sphere. The centre of each is composed of a poorly de-
fined, not quite homogeneous refractive substance, as in corresponding
stages of the first archiamphiaster.
The fibres joining the centres and together constituting the spindle
are, as usual, slightly curved, and they already present inconspicuous
thickenings in the equatorial zone.
The granulations of the vitellus, although for the most part evenly
MUSEUM OF COMPARATIVE ZOOLOGY. 203
distributed, show about the animal pole irregularities of arrangement,
which at first sight give one the impression that the outline of the outer
stellate sphere is not even. This is most noticeable when the view is
upon the animal pole, as in Fig. 24. However, the archiamphiaster, seen
in profile, shows — whichever way the vitellus is rotated about the spin-
dle axis — that this appearance is produced by aggregations of granules
quite outside the stellate sphere, and that really the surface of the latter
is not invaded by these granulations.
Inasmuch as the stage just described has not been seen by other
observers, it will not appeag superfluous to state briefly the evidence that
it is the second archiamphiaster. The stages with which this might most
easily be confounded are without doubt that of the formation of the jirst
archiamphiaster, and that of the jirst cleavage amphiaster.
1. The egg in question was one of four of nearly the same degree of
advancement (Figs. 25, 22, 23, 57). Three of these were subjected to
acid at intervals of ten minutes, the first (Fig. 25) being immersed on
the appearance of a conical protuberance ; the second (Fig. 22), though
ten minutes later, seems to have been hardly more advanced than the
first. This one (Fig. 23), the third, was observed to have a conical ele-
vation ten minutes before its immersion, although the elevation may |
possibly have first appeared a few minutes earlier. It must have been
then at the /east ten minutes after its appearance, and most likely
more, perhaps even fifteen or twenty minutes, when the conditions here
preserved became fixed. This in itself would be enough to preclude the
possibility of the first mistake, even if the first polar globule were no
longer to be discovered in contact with the vitellus.. There can be no
doubt, then, that the first polar globule had already been formed, and
that consequently the figure in question could not be the first archi-
-amphiaster.
2. The second possibility may not at first appear so easy of refuta-
tion. The position of the axis of the spindle relative to the already
formed polar globule, it is true, is little in harmony with the inter-
pretation of the figure as the amphiaster of the first cleavage sphere,
and is exactly what we might expect of a second maturation spindle.
Nevertheless, it might be urged that possibly the polar globule is no
longer located at that point of the vitelline surface where it originated,
and that consequently the relation of the spindle axis to the globule is
quite valueless in determining the nature of the spindle ; for in that case
the polar globule here figured might be the second, and the stellate figures
accordingly could only be interpreted as belonging to the first cleavage
2.04. BULLETIN OF THE
amphiaster. Aside from the fact that the egg in a living condition was
under observation at least some ten minutes immediately prior to its im-
mersion, during which time one could hardly have failed to distinguish
a fully formed first polar globule, had such actually existed, there are
other and sufficient reasons for construing the observations differently.
Not only that the comparatively large size of the polar globule points
to its being the first, rather than the second, and that a slight prolonga-
tion from one side (p) is evidence that it had not yet wholly severed its
connection with the vitellus, but it is especially the evidence within the
vitellus itself that makes the above interpretgtion inadmissible.
This can be understood only by reference to what will appear more
fully in speaking of the amphiaster of the first cleavage sphere; namely,
that the two stars of the cleavage amphiaster lie in a plane which is
perpendicuar to the animal radius at a point much nearer the animal
than the vegetative pole, and that they are of almost identical appear-
ance, though often deviating considerably from aspherical form. (Com-
pare Fig. 82.)
None of these conditions are fulfilled by the figure under considera-
tion. There is no evidence that any one of the lines perpendicular to
the axis of the spindle at its middle * terminates at the animal pole of the
vitellus ; and even if such evidence existed, the plane, which is perpen-
dicular to such line and also passes through both the asters, would not be
perceptibly removed from the centre of the vitellus. Moreover, while
the two stellar masses are almost spherical, — and therefore unlike that
which we might expect in the amphiaster of the first cleavage sphere
(compare Fig. 82),—they differ from each other in the sharpness of
outline already noticed, and thereby again fail to conform to the re-
quirements of the indicated interpretation. Other objections, drawn
from a comparison of this figure with the amphiaster of the first cleav-
age sphere, might be adduced in answer to the possibility of this ex-
planation ; but enough has been said already to place beyond doubt its
true nature; it is the amphiaster that immediately precedes the forma-
tion of the second polar globule.f
* It is at once apparent from the figure that no such perpendicular could be a radius
af the vitellus, from the fact that one end of the spindle is much farther from its cen-
tre than is the other. '
+ The possibility that one of the stars might be due to fecundation — might be the
so-called male aster — has not been overlooked. But the intimate union of the two
stars by means of a spindle which has an equatorial zone of granulations would make
this extremely improbable, even if the method in which the two pronuclei become
joined were less accurately known than at present. See pp. 224-229.
MUSEUM OF COMPARATIVE ZOOLOGY. 205
It is an important question, How does the second archiamphiaster
arise, and what relation does it bear to the first archiamphiaster 4
Very few observers have given this question special attention, and
those who have are not all positive in their opinions. According to most
of the descriptions given, the vitelline “half-spindle,” which remains
after the formation of the first polar globule, simply undergoes an
elongation caused by the gradual recession of the single remaining aster
from the surface; the internal zone of fibre thickenings disappears by
the distribution of its substance to form the lengthening fibres of the new
spindle; and there arises a second stellate figure whose rays converge
toward a point of the surface where the peripheral end of the spindle
remains. Such an origin could not be directly compared with the for-
mation of the first archiamphiaster, or subsequent amphiasters : it must
be at best a greatly abbreviated process, if at all comparable with the
ordinary method of amphiastral formation. In all other cases both cen-
tres of radiation arise as new differentiations in the protoplasm, and only
make their appearance when the nuclear substance has assumed a defi-
nitely circumscribed form ; in this case (according to the authors) only
one of the centres of radiation has the least claim to be considered new,
and the nuclear thickenings do not become fused into a definitely limited
nucleus.
The case (Fig. 23) to which I have called attention presents some
evidence that the second archiamphiaster is not formed in so direct
a manner as has been supposed. There is no absolutely incontroverti-
ble reason for denying that this complete amphiaster may have been
formed much in the manner above indicated for the incomplete one.
It would only be necessary to assume an extensive migration from the
surface on the part of the spindle and its asters, instead of a movement
on the part of the deep aster alone. There are, however, some objec-
tions to this view. The spindle has the appearance of being formed
in the ordinary way, rather than that of having its fibres drawn out ; it
is not so sharply defined as I should expect a spindle to be, if resulting
from a drawing-out process ; it is much broader, and its peripheral fibres
more abruptly bent, than would be the case in that event. The fact of
its being totally enveloped in the yolk is in itself more easily reconcilable
with its formation in a normal than in an abbreviated manner, since in
the former case the centres of radiation arise at points within the vitel-
lus, and thus is avoided the necessity of supposing that there is a cen-
tripetal migration of the spindle.
We have seen that at the completion of the first polar globule the
206 BULLETIN OF THE
lateral zone of thickenings belonging to the vitellus had already
reached the edge of the central “area.” The vitelline half-spindle
has been seen gradually to fade, but its complete disappearance I
cannot affirm from direct observation. It seems to me not entirely
impossible that its filaments are absorbed by the zone of thickenings,
and that the latter is actually converted, as in the normal method,
into a nuclear structure, in the vicinity of which two new stars (the
second archiamphiaster) make their appearance. Both of these (the
existence of a veritable nucleus, and the formation of two new stars)
are only assumptions. I have no direct evidence that such a nuclear
structure intervenes between the two archiamphiasters, nor that the two
asters are both formed about new centres. There are only very slight
indirect signs of such a condition, — indications that only warrant the
suggestion of a possibility. I will not on that account withhold the
observations.
There is some reason for believing that the view presented in Fig. 53
is that of the second archiamphiaster in process of a rotation which would
eventually have brought its axis into coincidence with the animal radius
of the vitellus.* If such be the case, it seems quite probable that this
whole figure originated from a nuclear structure, in much the same man-
ner as the first archiamphiaster is known to arise from the germinative
vesicle, and that consequently this second spindle was not durectly de- .
rived from the first spindle, and that possibly both of the stars are new
productions. The reasons already indicated for thinking it is the sec-
ond, are certainly only meagre evidence to fill the place of the more
complete observations which are needed, but may possibly suffice to
make probable what I have stated as my conviction, that the figure is
that of the second, and not of the first, archiamphiaster.
Perhaps the most noticeable feature of this amphiaster is the inclina-
tion of its axis to the supposed animal radius. This specimen is es-
pecially interesting, as it is the only one in which I have succeeded in
finding evidence of this obliquity. Such a peculiarity has often been
noticed by other observers in the case of the first archiamphiaster. It
will be’seen from Figs. 53, 54, that the spindle is not radzal in position,
The two asters are not of equal extent, the deeper being the larger.
Such a difference in sharpness of limitation as I have seen in cther cases
is not noticeable here, or at least it is much less marked than in many
instances. In neither star does the influence produce rays reaching to
the periphery ; in other words, the figure is wholly immersed in the
* See page 189.
MUSEUM OF COMPARATIVE ZOOLOGY. 207
vitelline substance. This in itself might have been a serious argument
against interpreting it as the second archiamphiaster, had I not already
shown from Fig. 23 the possibility of such a state of affairs. The
<centres of the stellate figures do not exhibit distinctly outlined “ areas,”
and the radiate fibres consequently become gradually lost in the central
darker portion.
I have spoken of the spindle; this exists potentially rather than for-
mally. The substance lying between the two asters is much clearer
than the surrounding protoplasm, that is, it is destitute of vitelline
granulations. Its outline, though not sharp and definite, is sufficiently
distinct to show that it has an almost spherical figure, tapering a little
at the poles. The fibres which help to make it conspicuous are not large,
nor are they evenly distributed through its substance. A view along
its axis (Fig. 54) shows that it is only the peripheral portion of the
spindle which is thus differentiated, and, further, that it is not devel-
oped alike on all sides. While the fibres on one side extend a third
of the way toward the axis, on the opposite side they form only a thin
layer. No median or lateral zones of thickenings are observable.
The impression conveyed by these observations is that the spindle
is not yet completed, that it is rather in process of formation, and that
the differentiation, commencing at the surface, advances with varying
rapidity toward the axis of the figure. If it were absolutely certain
that this is the second archiamphiaster, there would be little ground for
_ the belief that it was formed by a simple elongation of the half-spindle.*
In Fig. 55 the amphiastral figure has assumed a strictly radial po-
sition, and the peripheral star has already reached the surface of the
vitellus, where it induces a prominent protuberance. The inequality
of the two asters is more noticeable than in the formation of the first
polar globule, a phenomenon which must be prevalent if the superficial
asters and the resulting polar globules are proportional in size. What
Seems most peculiar in the outer star is the limited extent of the radial
influence on the side toward the centre of the vitellus, a feature not seen
in other figures at this stage.t The deeper star remains central in posi-
* There is hardly reason to suppose that the egg seen at Fig. 53 is so far advanced
as to present the amphiaster of the first cleavage sphere. Neither the stage of
development, as inferred from eggs of the same lot, nor the position of the figure
nor the inequality of the stars, seem reconcilable to such an interpretation.
T As indicated by a previous reference to this figure, the external aster presents
in a marked degree, when viewed from the animal pole, the peculiar spiral arrange-
ment of its radiate fibres which was seen in an early stage of the formation of the first
polar globule.
208 BULLETIN OF THE
tion and of wide extent ; its rays straight; its centre not quite homo-
geneous.
The spindle, especially, appears very different from the condition pre-
sented in the preceding stage. It is well defined, long, and embraces
few thick fibres, which are arranged in a close, narrow bundle. The
middle third of the fibres seems somewhat thicker than the terminal
thirds, but no other indication of either equatorial or lateral zones can
be made out. From the position of the centre of the outer radiate fig-
ure, which is still at some distance from the surface, it may be inferred
that the stage here shown antedates the formation of the equatorial
nuclear plate; however, the gradual thickening of the spindle fibres
toward the equator may perhaps be interpreted as a differentiation in-
itial to the formation of the plate.
The vitelline granulations, otherwise evenly distributed, are largely
excluded from the stellar areas, and are less numerous about the animal
pole than in the vegetative half of the sphere.
The phenomena connected with the production of the second polar
globule are, from this point on, nearly a repetition of those of the first |
globule : the formation of the equatorial zone and its separation into
halves ; the translation of the whole figure along the animal radius; the
ultimate attainment of the surface by the centre of the peripheral star ;
the consequent modification of its form; the deepening constriction
which cuts down upon the spindle between the two lateral zones ; the
formation of a cell-plate; the gradual disappearance of the half-spindle ©
in the polar globule, and a corresponding indistinctness in the vitelline
half-spindle, —all these occur, with only slight modifications, in the
manner already traced in the earlier stages.. There are, however, some
points worthy of more special attention. The second polar globule is
generally smaller than the first. The relative sizes, which are subject to
considerable variation, may be most easily comprehended by an inspec-
tion of the figures. Then, too, a certain obliquity of the parts about
the animal pole, already alluded to (p. 182), is often observable during
the formation of the second globule. This is well exhibited by Fig. 66.
The internal half of the spindle is so obliquely placed as to appear almost
parallel to a tangent at the animal pole; the long axis of the globule is
also oblique, but is oppositely inclined, so that a sharp bend is caused in
the course of the interzonal filaments. The centre of the deeper star
thereby attains a more superficial position than would otherwise be pos-
sible, and it may be that we are to look to this fact for an explanation —
of the peculiar appearance. I am inclined to think, however, that the
MUSEUM OF COMPARATIVE ZOOLOGY. 209
obliquity is more likely to have been produced by an inequality in the
constriction, just as in ordinary cleavage, where it is often found that
the Be Ascicn furrow advances from one side with much greater rapid-
ity than from the opposite. In a view at right angles to this (Fig. 67)
the spindle and globule are seen to be quite symmetrical, though not
strictly radial to the vitellus. I have so often observed this obliquity,
that, although certainly not to be considered as universal, I believe it to
be characteristic of this stage.
Another not less peculiar, though by no means constant phenome-
non, affects the inner star. During the formation of the second polar
globule, the radiate appearance in the vitellus becomes wider and wider,
until it at times is traceable to within a short distance of the periphery.
It is at the close of the formation of the second globule that it seems
to attain its maximum extent, — to dominate the whole vitellus. Lying
as it does, with its centre so near the surface of the yolk, the rays are
necessarily of very unequal length. That, however, is neither their most
noticeable nor most interesting peculiarity. Seen in certain favorable
positions, they are observed to stretch away toward the periphery, not
in rigid straight lines, but in bold, sweeping curves, which are so related
to each other that they present the appearance of extensive, more or
less sharply curved spirals. A view upon the animal pole affords a sur-
vey of the most extensive curves. Occasionally (Fig. 78) the course of
rays may thus be traced in a sweep of nearly 400°. Tracing them from
the centre of the star, these fibres may be seen to curve in a constant
manner, so as to be only slightly divergent. Finally, after completing
an immense arc, they become invisible near the surface of the yolk.
Such prominent fibres, however, do not describe their spirals in a single
plane, but, as the focusing of the instrument as well as side views teach,
they gradually descend toward the vegetative pole as they recede from
the centre of the star. Necessarily not all the rays of a given vitellus
are thus extensive, but ‘all show the curvilinear course more or less dis-
tinctly. In some cases the rays do not seem to centre in a common
point, but to arise along an axis, as in Fig. 66. The latter, however, is
not a straight line, nor even a simple curve, but shares in the spiral in-
fluence expressed in the rays in such a way as to have approximately
the form of a corkscrew. The dotted line a 8, Fig. 66, gives the projec-
tion of this corkscrew axis on the plane of the optical section.
Both the extent of the rays and the degree of their curvature are.
Subject to great variation in different eggs. The opposite extremes to
those just described are presented by Fig. 63, and all gradations be-
VOL. VI.— No. 12. 14
210 BULLETIN OF THE
tween these extremes are to be met with. Nor does it appear that
the direction of the spiral is constant, for, while my earlier observations
chanced on cases in which the course was left-handed, nie studies
taught that the reverse was not uncommon, though probably of less
frequent occurrence. ‘Thus far I have not seen this spiral arrangement
in the rays of the deeper star of the jirst archiamphiaster. On the other
hand, the spiral rays of the outer star, already seen in the case of the
first archiamphiaster, are often found in the second. No instance has
come under my observation in which this arrangement was traceable in
both stars of a given amphiaster.*
After the formation of the second polar globule, the influence which in-
duces the stellate figure seems to quickly wane ; for the rays become less
and less extensive, and finally altogether undiscoverable, — a fact which
may in some degree explain the differences of extent which prevail in the
stellar figures of eggs otherwise presenting apparently the same stages of
development.
The gradual disappearance of the deeper stellate figure is synchronous
with other processes most intimately associated with the fate of the in-
ner half of the second maturation spindle. Just as in the formation of
the first polar globule, so here one half of the equatorial zone of fibre
thickenings passes into the globule ; the other half remains in the yolk,
and moves along in the direction of the spindle fibres toward the centre
of the deeper stellate figure. This centre, however, it does not reach in
the condition of a group of thickenings, nor even soon after this form has
given place to a more definitely circumscribed structure.
There is formed, at the expense of this inner zone, upon the com-
pletion of the second polar globule, a vesicular structure of irregularly
spherical or ovoid form, which is at first homogeneous, or contains at
most only a few highly refractive spherical bodies of unequal size. It
is asserted that this structure is formed at the expense of the lateral
zone of thickenings, not because a direct metamorphosis in the living
egg has been observed, but rather as an inference from the fact that it
occupies the place of the latter near the centre of the stellate figure
when the zone as such has disappeared. Just what the relation of the
individual thickenings to the ovoid vesicle is, I am not able to say.
Either each becomes a centre about which is grouped a fresh accumula-
tion of substance that ultimately unites with neighboring like masses
to form the homogeneous contents of the vesicle, whose enclosed corpus-
cles (nucleoli) would then be identical with the spindle thickenings, or
* See p. 535.
MUSEUM OF COMPARATIVE ZOOLOGY. Zi
the thickenings first unite to form a homogeneous mass, in which new
bodies arise as nucleoli. A few facts seem to point to the latter as the
more probable explanation. J have rarely seen a case, it is true, in
which this vesicular structure was entirely homogeneous (Fig. 70°); yet
the small number of the enclosed bodies in the earlier stages, as well as
their noticeable inequality of size, are facts not easily reconciled with
the notion of a direct conversion of the thickenings into nucleoli. The
constant increase in the number of these corpuscles indirectly favors
the idea that a// are new productions within the homogeneous nuclear
mass.
For reasons which are already familiar to those acquainted with
the phenomena of this stage of development, and which will be consid-
ered later in the present paper, this vesicular structure will be called the
female pronucleus (fpn), and the contained bodies female pronucleoli
(fpnl). The opacity of the yolk prevents observation on the living egg
of the changes which accompany the origin of this pronucleus ; so that the
conclusions are necessarily of the nature of inferences, capable, however, of
some degree of control. As previously stated, the earliest stage showing
unequivocally the existence of this pronucleus is one in which pronu-
cleoli are already present. But in some eggs, as in that represented
in Fig. 63 (compare Fig. 70°), a confused mass occupies the place of the
lateral zone of thickenings, and may fairly be taken, I believe, as the in-
cipient stage of this pronucleus, which does not as yet show any distinct
traces of nucleoli. Treatment with osmic acid is generally much more
setviceable for the discovery of this pronucleus than that with acetic
acid. Possibly this may explain why some of the eggs subjected to the
latter do not exhibit any distinct evidence of the lateral zone, or the
pronucleus (Figs. 66, 67), when, to judge from other features, we might
look with confidence for such structures.
Ata later stage (Figs. 57-60) this female pronucleus is found still
occupying a position near, but certainly not coincident with, the centre
of the stellate figure. Its outline after treatment with acetic acid is
quite distinct, and exhibits a double contour, which is usually more or
less wrinkled (Figs. 57, 59). After treatment with osmic acid, however,
the outline appears even, and there is no double contour to suggest
the existence of a distinct nuclear membrane. In both methods of treat-
ment followed by staining, the pronucleus is somewhat more deeply
colored than the surrounding protoplasm ; especially is this noticeable
in the osmic acid treatment. By either method it contains a number of
rounded bodies, varying from 2 » to a minuteness bordering on the lim-
212 BULLETIN OF THE
its of discernment with Hartnack, obj. 7, oc. 4. These contained bodies,
or nucleoli, are very strongly refractive, and consequently appear as
brilliant and conspicuous objects within the pronucleus, especially when
treated with osmic acid followed by carmine staining. They are not
always evenly distributed through the pronucleus, but are often grouped
in different parts of its substance. No considerable portion of the pro-
nucleus, however, is destitute of nucleoli.
The extent to which the inner star of the second archiamphiaster con-
tinues to hold sway in the vitellus is subject to variation. Often it is
seen still at its maximum after the female pronucleus has acquired a
diameter of 15 » or 20 p. At other times it is much less extensive
(Fig. 63), even at the beginning of the formation of the pronucleus.
The latter unquestionably continues to increase in size, and sometimes
retreats a little from the animal pole of the yolk toward its centre ; more
often, I believe, it remains quite near the surface, — at the place it oc-
cupied when the confluence of the thickenings began.
Simultaneously with its increase in dimensions occurs an increase in the
number of nucleoli. How the new nucleoli arise — whether by division
of those previously existing or not — must, in default of direct obser-
vations, remain undetermined ; yet the entire absence of forms showing
any of the stages of division affords no support to the supposition of
such an origin. There are, itis true, some deviations from this relation
between the increase in the size of the nucleus and the increase in the
number of nucleoli (Figs. 70, 77); but, in general, I think the cor-
rectness of the statement cannot be doubted. It is also quite certam
that the size of the larger nucleoli is directly proportional to the size of
the pronuclei themselves ; so that a growth concomitant to that of the
pronucleus may fairly be assumed. The nucleoli appear perfectly homo-
geneous, and very prominent in osmic acid preparations; in acetic acid,
on the other hand, they are less distinct, and on the average somewhat
larger. The outline, even with the latter method of treatment, remains
full and entire, and in some cases it appears double ; but nothing like
a double contour is seen in preparations with osmic acid. Neither
vacuoles, nor granulations, nor punctations, are discernible within the
nucleoli by any method of treatment employed.
The changes which further affect the female pronucleus are rather
those of growth than of migration. It is especially significant that
this female pronucleus remains constantly near the surface of the vitel-
lus. However much it may increase in diameter, its removal from the
animal pole is never great, in most cases altogether inappreciable.
MUSEUM OF COMPARATIVE ZOOLOGY. 213
Owing to its increase in size, one of its margins may even come into
closer proximity to the surface at an advanced stage than at an earlier
one. Its relation to the centre of the vitelline star now in course of
disappearance is hardly less interesting and important. It has already
been stated that the female pronucleus is not formed at the centre of
this stellate figure. It might be added, there is strong ground for be-
lieving that it never comes to occupy such a relation to the radiating
fibres left in the vitellus after the detachment of the second polar globule.
Certainly, in advanced stages of its formation (Figs. 57, 59, 68), this
centre of radiation is distinctly outside the boundary of the pronucleus,
— to say nothing of the coincidence of their centres, — and often at a
considerable distance from it. It may be here remarked concerning the
last trace of the second archiamphiaster, that the rays of its internal
star fade away so gradually throughout their whole length that it is
often quite as difficult to distinguish them near their point of con-
vergence as at any other part of their course. Compare Fig. 59:
The diameter of the female pronucleus may eventually attain one
fourth the diameter of the whole vitellus (Figs. 73, 74, 77), or even in
some cases a third of its diameter (Fig. 85).
When treated with acetic acid its shape .is extensively modified by
deep and numerous wrinkles and folds which have a very characteristic
appearance. ‘The outlines are usually more or less concave outwardly,
as though caused by the thrusting outward of some angular contained
body; yet the protruding points are not sharp, but close to the
apex become rounded, so that really there are no “cusps” formed by
adjacent curves, as one is inclined to think at first sight (Figs. 59, 80,
85, etc.). The outline becomes more irregular and wrinkled in advanced
stages of the nucleus. In this method of treatment, too, the outline
constantly appears double, and increases in distinctness in proportion
to the size of the nucleus. Within the latter, one distinguishes in
advanced nuclei a large number— up to fifty or sixty —of nearly
spherical bodies, the pronucleoli, which often exhibit double contour
lines. I have never seen one of these nucleolar bodies sufficiently dif-
ferent from the others in size, or behavior with reagents, to warrant the
distinction of a main and accessory nucleoli; and only once (Fig. 52,
chromic acid preparation) have I seen anything like a nuclear reticulum.*
When treated with osmic acid and subsequently stained in carmine,
* P. S. In eggs of an undetermined species of Limax I have observed in both fe-
male and male pronuclei a single nucleolus of much greater size and more deeply
stained than the oper nucleoli. Compare Figs. 80, 80¢, and explanations.
214 BULLETIN OF THE
the female pronucleus presents a different appearance, one which in some
respects doubtless reproduces the natural condition more truly than the
acetic acid process, though in other points it may be doubted if it does
not offer quite as much violence to nature as the latter. The pro-
nucleus, far from being wrinkled, presents a most delicate and even
outline, which seldom deviates from a continuous and often exquisite
curve. It often approaches a spherical form ; at other times it is ovoid,
or may even be pear-shaped (Figs. 68, 77, etc.).
From a large number of comparisons, the conclusion seems reasonable
that, treated in this manner, the pronucleus, though very likely ap-
proaching quite nearly the form and proportions which it had in the
fresh condition, nevertheless has suffered an absolute reduction of size
much greater than in the other method of treatment, and somewhat
greater proportionate diminution than the vitellus. The same, too, is
doubtless true of the pronucleoli.
No trace of a double contour can be found by the osmic acid method,
either for pronucleus or pronucleoli. The substance of the nucleoli, as
well as that of the pronucleus in which they are imbedded, appears per-
fectly homogeneous with the highest power used. (Hartn., obj. 9, oc. 4.)
The nucleoli, as before, appear to vary somewhat in size, but are uni-
formly much more prominent than when treated with acetic acid.
They present a rounded form, but do not approach so closely that of
the sphere as in acetic acid specimens, and they show the same want of
regularity in arrangement that has already been noticed.
In proportion to its service in making prominent the nuclear struc-
tures, osmic acid fails to be of value in making distinct the radiations
of the vitellus which characterize different stages in the development.
Some traces of the stellate figures may usually be made out, but they
are never present in that unequivocal boldness which belongs to acetic
acid preparations.
The female pronucleus often lies in such close proximity to the sur-
face of the vitellus that the latter becomes involved in its extensive
foldings, and consequently shows corresponding wrinkles and depressions
(Fig. 73). Ina more marked degree something of a similar nature has
taken place in a few of the specimens treated with osmic acid (Figs. 69,
75). In these cases, however, there is not a general wrinkling of the
pronucleus. The nearest portion of the vitelline surface appears as
though forced inward like a hollow plug, thus causing a corresponding
depression in the outer half of the pronucleus.
Sometimes there is a similar plug-like projection from the opposite or
MUSEUM OF COMPARATIVE ZOOLOGY. 215
deeper face of this pronucleus, which in turn impinges on a second
similar body. The origin and destiny of the latter will form the subject
of subsequent considerations. Thus, in optical section, one or both of
these pronuclei appear to have the shape of a crescent, with blunt
rounded horns. In these cases, caused, probably, by too prolonged or
vigorous action of the acid, the contents of the pronucleus are altogether
homogeneous, and without any trace of nucleoli, notwithstanding the
size of the pronuclei. Iam at a loss to explain this disappearance of the
pronucleoli. There is only one, not altogether satisfactory explanation
that has occurred to me. I have already stated my conviction that the
nucleus becomes more contracted by treatment with osmic acid than
when hardened in acetic acid. This diminution of size may best be
accounted for on the supposition that it suffers a loss of fluid compo-
nents, — becomes more concentrated, and compact. If such an as-
sumption is legitimate, it is at least possible that the above-described
condition may have been brought about by so prompt and considerable'a
loss of nuclear fluid as to make the substance of the nucleus very compact
and refringent, — so refringent, in fact, as to leave no perceptible differ-
ence between the nucleoli and other parts of the substance of the nucleus.
Another possible assumption is, that the nucleoli were already dissolved
in preparation for the coming metamorphosis into a nuclear spindle.
Ed. Van Beneden (’75, p. 698) has observed something which I am
inclined to think is very like what I have described, if not indeed
identical with it. I am not able to speak with the greatest certainty,
since the description referred to is not accompanied by figures, but I am
the more inclined to think the phenomena are identical, because Van
Beneden in this case also employed osmic acid. I shall recur to this
point again.
II. FEcuNDATION.
In eggs examined soon after extrusion there are to be observed in the
vicinity of the vitellus a number of small ovoid bodies, which are at once
noticeable from their possessing considerably greater refractive power
than the surrounding albumen. (Fig. 49.) These bodies are of even
outline, about 10% long and 7 to 8 wide. The greater number usually
lie near the vitellus, some apparently in contact with it, while numbers
are scattered irregularly in different s of the albumen. Among
these may usually be found some which have a filamentous structure
protruding from one side. On further inspection it will appear that the
remaining portion is of the same nature, but from the closeness of the
216 BULLETIN OF THE
coils the filament is easily overlooked, except when the uncoiling is
already begun. At a somewat later stage the uncoiled filaments out-
number the oval bodies, and still later few or none of the latter are to
be found. The oval bodies are unquestionably single coiled spermatozoa
which suffer an unfolding and at length lie in the food-mass as out-
stretched male elements. They are often wrapped about the vitellus,
at other times thrown into irregular curves in the surrounding albumen.
The unfolding must be slow, for I have repeatedly watched in order to
discover the nature of the process, but have never succeeded in seeing
motion, either in the oval bodies or in the outstretched spermatozoa.
I have never failed to find spermatozoa when made an object of special
search. In some cases they are present in great quantities, even forming
extensive trains through different parts of the albumen.
Neither the growth nor the structure of the spermatozoa has been
made the subject of extended observations. As regards their form it
may be seen from Fig. 94 that they are thread-like, gradually tapering
from immediately behind the “head ” to the opposite extremity. They
may attain a length nearly equal to the diameter of the vitellus. The
‘“‘head ” is flattened, oval, somewhat pointed at its free end, and when
seen sidewise appears tongue-shaped and joined to the neck at a very
slight angle. The portion following the head has often a wavy course,
while the terminal part frequently remains in a loop.
I once saw quite distinctly an interesting spermatozodn in the albu-
men of an egg already treated with reagents, and made at the time
(Aug. 15, 1878) a hasty sketch, which I have had reproduced in Fig. 94,
since it indicates the existence of an undulating membrane. So far as I
am at present aware, this has never been observed before of the sperma-
tozoa of slugs. Leydig (Lehrbuch d. Histologie, p. 533) says that hith-
erto (1857) zodsperms with undulating membrane have been found only
in the cases of Rotifers and Cypride. Whether we have to do in the
case of Limax with dimorphic forms of the spermatozoa, I cannot say,
as I have given the subject no attention. The spermatozodén here figured
was motionless, so that I can only infer that the membrane figured un-
dulates in the active spermatozoon, after the manner known in the sala-
mander and other animals. The loop at the end of the tail in this case
seems to be very delicate; perhaps it is formed exclusively by the thin
membrane.*
* Sept. 1, 1880. Gibbes (780) has recently demonstrated the existence of the
vibratile membrane in the case of several vertebrates, and some invertebrates.
Among the latter is Helix ; I am thus the more confident that it is really an un-
dulating membrane which I have seen in Limax.
MUSEUM OF COMPARATIVE ZOOLOGY. 217
No motion in the spermatozoa having been seen, their direct penetra-
tion into the vitellus is necessarily beyond the observer’s experience;
nor has anything been observed in the living egg at this early stage to
indicate that penetration had taken place. Nevertheless it is highly
probable, judging from the observations that have recently been made
in cases more favorable for the study of this phase of development, that
the substance of at least one of these thread-like spermatozoa is already
embraced within the vitellus at the time the egg is laid.
The earliest indication observable in the living egg which can be
referred even indirectly to the presence of a spermatozodn occurs some
time after the formation of the second polar globule.
Allusion has previously been made to the fact, that after the forma-
tion of what has been called the female pronucleus there appears a sec-
ond structure of similar aspect. The latter is situated at quite a distance
from the former, and is often more deeply imbedded in the vitellus, on
account of which it is usually less distinct (m. pn., Figs. 65, 30). After
a time it is found nearer the female pronucleus, and in proportion as it
nears the latter it becomes larger and more easily seen. At length
the two lie side by side, but still continue to increase in size. I have
not been able to make out any constant difference in dimensions between
them ; it is therefore often quite impossible to say which is the female
pronucleus, and which the other body, unless they have been under ob-
servation for some time previous to their contact. The latter has
quite the same appearance as the female pronucleus. Its study in the
living egg is permitted only occasionally by an exceptional transparency
of the yolk. Under favorable circumstances its outline is seen to ex-
hibit slow changes of form such as have already been described for the
female pronucleus. In its growth it keeps pace with the latter. In
some cases considerable portions of their surfaces appear in contact. In
others, however, even when of great size, they are only very close to
each other, and do not touch.
The meagre results to be obtained from the study of the living egg
are very well supplemented, in some points at least, by that which may
be learned by other means of investigation. The use of osmic acid is
more satisfactory than any other single method. I have not had the
Same success in the use of acetic acid, since it does not cause the vitel-
lus to become as transparent, nor are the nuclear structures made so
conspicuous by it. To the fact that osmic acid was used much less
frequently than acetic acid is probably due my want of success in de-
tecting this nuclear body at an earlier stage in its formation.
218 BULLETIN OF THE
In no case have I found any evidence of the existence of this body
before the formation of the second polar globule. However, there is
always to be found in hardened eggs, as soon as the female pronucleus
has become well marked, another structure resembling the female pro-
nucleus (Figs. 58, 60), which is usually located at some distance from
the animal pole.
It ordinarily has almost exactly the same size as the female pronu-
cleus, and deports itself quite the same as the latter, when treated with
different reagents. From its position it is unquestionably the deeper
clear spot discovered in the living eggs. In the earliest condition in
which it has been satisfactorily observed, it has, with a single exception
(Fig. 70°), already attained a considerable size, and contains a number of
highly refractive spheroidal bodies. It is found at this stage (Fig. 60)
still not far removed from the surface of the vitellus. It becomes visible
in the liwng egg only at a later period, when it has altered its position
and attained greater dimensions.
From its subsequent changes and ultimate fate there need be no
hesitancy in calling it at once the male pronucleus (mpn), even though
its relationship with a spermatozoon could hardly have been surmised,
but for the very conclusive observations made by several observers
within the past few years,—one might almost say months. In a
few cases toward the close of the constricting phenomena, which set
at liberty the second polar globule, and before a distinct female pro-
nucleus had appeared, I have noticed, very close to the surface of the
vitellus in the vegetative hemisphere, small vacuoles (diam. 6 p) of
homogeneous appearance (Fig. 66), which I am inclined to consider as
earlier stages in the existence of the male pronucleus. The prepara-
tions were all such as had been produced by the use of acetic acid and
subsequent staining in Beale’s carmine, which, as before stated, is less
favorable for making conspicuous the pronuclei than is the osmic acid
process. The interference of the granular elements of the yolk is such
as to make the observations on these small structures exceedingly diffi-
cult and little reliable, for which reason it may be better to consider the
object seen as only possibly bearing the interpretation suggested. The
doubt as to the significance of these structures was further increased
by the fact that in one case—the one figured —¢wo such vacuoles
of almost identical appearance occurred in remote parts of the same
vegetative hemisphere. It might not be absolutely impossible, it is
true, that these vacuoles resulted each from the presence of a sperma-
tozoon, but it would be highly improbable, in the light of all that has
MUSEUM OF COMPARATIVE ZOOLOGY. 219
recently been learned concerning the relation of egg and spermatozoon.
In one other case, alluded to above, a perfectly homogeneous oval vacuole
(Fig. 70°, 8) was observed near the surface of the yolk at the equator.
The female pronucleus of the same egg (Fig. 70°, a) was of nearly the
same size, but contained a single large nucleolus. In all cases the vacu-
ole seemed filled with a substance of less density than the surrounding
portions of the vitellus.
As already indicated, the male pronucleus in its more advanced stage
is so nearly similar to the female pronucleus in all morphological
points, that it would be mere repetition to describe it in detail. Not
only the size of the two at any given time, but also the form, the char-
acteristic behavior with different reagents, the appearance of the nucleoli,
even the number of the latter, are subject to such unimportant differences
that it would be quite impossible for one, however familiar with them, to
say which was the male and which the female element, were it not for
the positions which they occupied relative to each other and the remain-
ing parts of the vitelline sphere.
Inasmuch as there exists a definite relation between the size of these
pronuclei and their distance apart, — which may be expressed by say-
ing, the larger the pronuclei, the nearer they will be to each other, —
it might be justly inferred, even without the corroborative evidence of
direct observation in the eggs of many other invertebrates, that migra-
tion of one or the other of them takes place. From what has already
been said of the migration of the female pronucleus, it may at once be
inferred that this approximation takes place principally, if not exclusively,
by a change in the position of the male pronucleus.
When within a short distance of each other, the two (Fig. 68) are
often seen with their more pointed ends directed toward the centre of a
stellate figure. In case acetic acid has been used, the form becomes
much altered, and it is no longer possible to observe so clearly this con-
dition ; but even here their mutual] relationship to the stellate figure may
often be very easily demonstrated (Figs. 57, 59).
Notwithstanding that in many cases this position may be shown, even
in an advanced state of the pronuclei, in other cases the female pronu-
cleus appears to be more or less coincident with the central portion of
the stellate figure (Fig. 72), although it probably never happens that
the centres of the two structures exactly coincide. In reality this aster
often becomes quite invisible before the close approximation of the two
pronuclei has been effected.
There may then be left for a time an irregular area in its place, where
220 BULLETIN OF THE
the coarser granular elements of the yolk do not intrude (Fig. 70), but
subsequently the force that kept these granulations back seems to yield
completely, and no part of the vitellus remains absolutely free from
them.
A condition such as is presented by Fig. 68 might leave one in doubt
whether this aster belonged to the male or the female pronucleus. A
comparison with numerous other cases (e. g. Fig. 72) leads me to think
there is no room to question its being an archiaster, —the remnant of
the inner star of the second archiamphiaster.
When it has attained considerable size, and is consequently in the vicin-
ity of the animal pole, the male pronucleus may sometimes be seen in the
living egg. In some cases, either from the comparative absence of yolk
granules, or from its superficial position, or from both, it may be easily
distinguished as a sharply marked spheroidal body (Figs. 21, 30), although
nucleoli are not always distinguishable. Infact, both the male and female
pronucleus — the latter more superficial, and the former somewhat deeper
— were seen and figured in Limax as long ago as 1850 by the Russian
naturalist Warneck (50, Taf. IV. Fig. 10’); although the state of em-
bryological science at that time did not allow this very accurate observer
to interpret his observations as successfully as may be done to-day.
The pronuclei ultimately come in contact, and their increase in size
does not seem to cease when they touch. They become more or less
flattened against each other, but an actual union, as observed in the case
of many other animals, is not to be seen here. If it ultimately takes
place, as we must conclude it virtually does, the union is so late and so
involved in other phenomena as to become entirely unrecognizable as
such. It is, therefore, at this point that the egg of Limax presents one
of its most interesting and instructive phases. Before proceeding to
consider these changes, which belong strictly to the process of segmenta-
tion, it is desirable to say a few words concerning some appearances
which must doubtless be considered abnormal. Although the observa-
tions are meagre, a brief statement of them may be welcome, since, as
far as I am aware, no one has recorded similar observations concerning
the eggs of Limax, nor indeed of any of the Mollusks.
For one interested in recent observations upon impregnation the de-
scription of the male pronucleus cannot fail to be of interest in a nega
tive way, inasmuch as no allusion has been made to the existence of any
special arrangement of the protoplasmic substance immediately surround-
ing it. It has been ascertained by several observers, that, in many ani-
mals, the male pronucleus early becomes, if not the centre, at least the
MUSEUM OF COMPARATIVE ZOOLOGY. 2aL
region of a special stellar structure, which extends in all directions
from the pronucleus, and which has a separate origin from all the
stellate structures connected with the production of the polar globules.
To this star has been given the name (Fol, 77*, p. 360) male aster.
It therefore seems remarkable that this structure, which I have called
the male pronucleus in Limax, should not be accompanied by some trace
of the characteristic star. This would have afforded grounds for appre-
hension lest my interpretation of this nuclear body might be erroneous,
were it not that the structure of the body, and its deportment under the
influence of reagents ; its growth, ever parallel to that of the female pro-
nucleus; its migration toward, and finally its contact with, the latter,
pointed unequivocally to its nature as the male element. In no case,
by whatever method treated, was any trace of such a stellate structure
in the protoplasm surrounding the male pronucleus to be detected,
either in its earlier or later stages, although carefully sought for in all
the numerous specimens of this age which have come under my observa-
tion.*
It is, therefore, a matter of interest, that a single egg (Fig. 81), which
must probably be considered abnormal, should afford the only trace of
‘what is so common to the male pronuclei of eggs in other animals. In
this specimen, beside an extensive system of delicate rays which cen-
tres near an irregular body that may possibly be the female pronucleus,
there are no less. than half a dozen other systems of rays, varying some-
what in size, distributed through the protoplasm of the vitellus in such
a manner as not to be very close to one another, nor yet very near to
the surface of the yolk. Each of these smaller stellate figures is com-
posed of a few prominent short rays, directed toward a central, homo-
geneous body of small size. After studying the observations of Hertwig
and Fol (77°, p. 469), it cannot be doubted that this is probably a
case in which numerous spermatozoa, instead of a single one, have
effected an entrance into the egg, and that their number must have been
at least as great as that of the observed smaller stars, whose central cor-
‘puscles may therefore be considered incipient male pronuclei. In the
immediate vicinity of the largest aster are to be found two or three
other nuclear elements, of which certainly one, and possibly two, occu-
pies the centre of its own special system of rays, now considerably ob-
scured by the predominance of the larger system with which it has
become confused. In the case of the nearer one, the appearance is much
as though a union with the female pronucleus were being effected. The
* The only possible exception has been explained above, p. 220.
222 BULLETIN OF THE
latter exhibits no indication of nucleoli.** The egg was treated with
acetic acid, and subsequently stained in Beale’s carmine.
III. CLEAVAGE.
The living egg has been followed in its changes through the formation
of two polar globules and the subsequent growth and approximation of
two nuclear bodies, the so-called male and female pronuclei.
These nuclei remain near the surface at the animal pole. They may
be distinguished in the living egg as two distinct bodies up to within a
short time previous to the rapid changes of the first cleavage. Shortly
before that event, their outlines are no longer discoverable in the fresh
egg. ‘The region remains more clear, but all that can be distinguished
is a more or less circular, ill-defined area, which is less opaque than the
surrounding portions of the vitellus. After a few moments, this area
grows less distinct. It finally appears elongated. Very soon this
lengthening has resulted in two light spots, which are inconspicuous
at first, but which increase in size and distinctness, and at length
become oval (Fig. 31). The long axes of the ovals are so directed that,
if prolonged, they would meet a little way beyond the animal pole of
the yolk.
During the earlier part of this series of proceedings, — viz. soon after
the meeting of the two pronuclei, — there is usually an accumulation of
transparent protoplasm about the animal pole; or, in other words, the
granules of the vitellus vanish from this portion of the yolk, leay-
ing sometimes a very thick superficial layer (Fig. 70°), at other times
only a comparatively thin covering, of clear protoplasm. This surface
layer may occasionally be traced quite around the yolk ; in other cases,
it can be followed for only a short distance from the animal pole.
If the outline of the egg be carefully watched about the time of
the formation of the two new light spots, it will be seen gradually
to lengthen in a direction corresponding to the line which joins the
spots (Fig. 31). As the latter enlarge, the lengthening increases, though
not very conspicuously. At length a slight flattening of the surface
appears just under the polar globules. This finally changes into a very
shallow depression (Fig. 37), which grows deeper (Fig. 32), and becomes
angular. If the yolk be viewed along the polar axis at this time, it will
* It is possible that the body I have called male pronucleus (mpn?) may repre-
sent the female pronucleus, in which event the structure marked /fpn? might be only
the ‘‘area” of the deep star of the second archiamphiaster.
™”
MUSEUM OF COMPARATIVE ZOOLOGY. 223
be seen to be considerably flattened parallel with the plane passing
through the animal pole and the two spots. The latter appear in this
position transversely oval.
A little later, the furrow will be seen to have extended around on the
sides of the yolk as a shallow depression, reaching something more than
half-way toward the vegetative pole. The oval spots have meantime
been ‘increasing in extent, and their axes have now (Fig. 32) become more
nearly parallel. In some cases one may see a faintly but unmistakably
radiate arrangement of the vitelline substance around these oval spots
as centres (Fig. 32). More frequently the yolk is too opaque for that, or
even for the detection of the oval spots. Soon after the appearance of
the depression at the animal pole, — within four or five minutes at the
usual temperature of a summer day, — the furrow has run quite around
the yolk, and now appears at the vegetative pole as a very broad, shallow
depression (Fig. 35). This annular constriction now deepens on all sides,
but most rapidly from that of the animal pole. Thus the axes of the
two clear spots become first parallel, and then somewhat divergent toward
the animal pole. But when the furrow of the animal half has advanced
to near the middle of the yolk, it has become narrowed, by the approach
of the opposing faces of the incipient spheres, almost to a fissure (Fig. 62*),
whereas the depression from the opposite side is now a broad groove, so
that the axes of the two clear spots have by this means become again
convergent toward the animal pole. By the further deepening of the
constriction on all sides, there are formed two equal, symmetrical, ovoid
bodies, which are connected by only a slender thread of protoplasm,
situated much nearer the vegetative than the animal surface (Fig. 62°).
The long axes of the new spheres are at this moment (before complete
Separation) directed convergingly toward a point in the plane of division
which lies in the prolongation of the animal radius. At this time, too,
the blunter end of the new spheroids is the one corresponding to the
vegetative half of the unsegmented yolk. Seen along the animal radius,
they appear elongated in a direction perpendicular to the line joining
their centres, and the surfaces which face are less convex than those
which look outward. A plane perpendicular to that of cleavage, and
coinciding with the animal radius, would divide each into symmetri-
cal halves. There is no other plane which could accomplish a like
result,
At length the slender filament becomes more attenuated, and finally
parts. The cleavage is accomplished ; but each of the spheroids still
continues to undergo further changes of form, and promptly assumes
224 BULLETIN OF THE
new attitudes towards its fellow.* Alterations within the yolk are not
easily observable. The light spots grow somewhat less distinct, but
further than this nothing can be seen.
In returning to the study of the normal course of development of
hardened eggs, I begin at the point where its consideration was left for
the purpose of presenting the abnormal conditions shown by the presence
of a number of spermatozoa in a single yolk.
In the eggs of most animals the pronuclei, after attaining their maxi-
mum size and coming into close contact, suffer a mingling of their sub-
stances by the disappearance of the limiting envelopes (membranes) that
for a time separated them. This union becomes so complete that authors
speak of the resultant structure as a single body, —a unit, which has
been called the nucleus of the first segmentation sphere. In the case of
Limax, we find that this unit structure is sought with very questionable
success. The first cleavage nucleus does not have a morphological existence.
I seek an explanation of the fact by assuming that the acceleration at
this stage of the ontogeny is so great that the division of this promised
structure is begun before it has an actual independent existence. To
say the least, the first evzdences of the coming separation of the yolk
have already made their appearance, while there are still two distinctly
separate pronuclei. I refer in these evidences to the new stellar shapes
which arise in the protoplasm of the yolk in the vicinity of the two pro-
nuclei, and which are destined to become the amphiaster of the first
cleavage sphere. Undoubtedly, the two new centres of activity which
now come into existence are only a part of a continuous process of trans-
formation which neither begins nor ends with them, — a process which
slowly obliterated the great spiral archiaster, and which will in turn
cause them to disappear; but it is equally certain that they belong
strictly to the phenomena of the first segmentation. In their beginnings,
these new centres exert an influence which, though not far reaching, is
vigorous and aggressive. All observations hitherto agree in making the
visible changes connected with these two centres synchronous in their
appearance ; and this may well be true for the majority of cases. It,
however, is not universally so, for in several of my preparations (Figs. 52,
73, 79, 80) very satisfactory evidence is afforded that one of the new
centres may exert an influence of considerable extent before its mate
has produced the slightest visible sign of its existence.
Usually these new stellar figures centre at points on, or very near, the
* The mutual flattening of the products of segmentation, and other interesting
phenomena of the same period, cannot be considered in the present paper.
MUSEUM OF COMPARATIVE ZOOLOGY. 225
surface of one or both the pronuclei. Most observers locate the two
points very definitely: both stars are made to lie in the plane along
which the two flattened pronuclei are at first in contact and then con-
fluent, and they are represented as occupying two diametrically oppo-
site points in the circumference of that plane. From this it follows that
_ the new centres are made to lie in the surface of the new nucleus (or
nucleus of the first cleavage sphere). However it may be in other cases,
it no longer holds good as a distinctive position for Limax. Unexcep-
tionally, there is a more or less marked antipodal relation expressed in
the position of the two new centres ; but they are not uniformly im con-
tact with, nor even in close proximity to, either of the pronuclet (Fig. 85),
and when such approximation does exist (Figs. 52, 74), it may be that
one of the new centres ts in relation with only one of the still separate pro-
nuclei. So great an ontogenetic concentration as the contemporaneous
existence of the archiaster and one or both of these new asters has never
been observed. The question may arise whether the single centres of
radiation above mentioned (Figs. 52, 73, 79, 80) may not have been the
last remnants of archiasters, since the latter persist for a long time. I
think the answer may be most positive that they are not ; for the archi-
aster fades gradually in all parts, and if the central portion remains visi-
ble a trifle longer than the rest, it is only as a very indistinct structure.
But the asters which concern us now are vigorous, though not yet of
extensive influence ; they are sharply marked by rays of comparatively
limited extent. Furthermore, their positions are not favorable to such
an interpretation. They are uniformly nearer the middle of the vitellus
than are the centres of the pronuclei. There is, however, some varia-
bility in the closeness of the latter to the surface of the yolk, which is
manifest in both fresh and hardened specimens. The two light spots
seen in the living egg, just prior to and during the first segmentation,
appear from their positions to coincide with the asters.
The condition of the pronuclei at the time of the origin of these new
centres and during their increasing ascendency is of special interest.
As has been already indicated, it is very difficult to prove in eggs
treated with acetic acid that there is a direct union of the pronuclei.
Even in cases where the amphiaster of the first cleavage sphere has
acquired a considerable extent (Fig. 85), it is clear that the two pro-
nuclei have not become fully amalgamated into a single structure, and
it may possibly be questioned if any portions of their substance have
become confluent. The nucleoli, though more faintly Saye ae than in
an earlier stage, are still easily recognizable.
VOL. VI.— NO. 12. 15
226 BULLETIN OF THE
At somewhat earlier stages (Figs. 73, 74, 79, 80), the nucleoli are
found to be very numerous. As many as sixty have been seen in a
single pronucleus, but generally about thirty are embraced in each of
the pronuclei. The variations in size are considerable in the same pro-
nucleus, and the average size is often noticeably different in those of
different eggs.
Both pronuclei continue to exhibit a double contour (when treated with
acetic acid) even after the appearance of the asters of the cleavage sphere.
The outline is much wrinkled (Figs. 73, 74, 79, 80, 85). Usually at the
time of the first appearance of the new asters the pronuclei are close
together, and it is difficult, by reason of their foldings, to determine how
extensively the two bodies are in contact. In a few cases there could be
no doubt in the matter, as the nuclei were in contact at only a single
point, or not at all. The specimen shown in Fig. 79 must have been
hardened very early in the formation of the new amphiaster, as only one
of the asters is visible. In the more advanced stage represented in
Fig. 85, the extent of the contact is certainly much greater, and the dis-
tinctness of outline along the contiguous faces so much impaired as to
leave the impression that a fusion of nuclear substances has already
begun. In the vicinity of this plane of contact there are to be seen in
each of the pronuclei a few highly refractive granules much smaller than
the pronucleoli, and not arranged in any discoverable order. Aside from
these two sorts of contained structures, the contents of the pronuclei
remain, as before, homogeneous.
The first cleavage amphiaster, in the earliest conditions seen, consists
either of a single stellar figure, or of two, quite limited in extent. The
rays are fine and approach the common centre so closely as to leave only
an exceedingly small area of homogeneous appearance ; in some cases,
indeed, it is impossible to make out such a definitely circumscribed por-
tion. The absence of a distinctly marked area is not confined, however,
to the early stages of the amphiaster. Eggs present in this respect
individual differences, so that in one the area may be seen with great
distinctness, and in another of the same age be indistinct ; even in the
same amphiaster one aster may show no line of demarcation about its
central area, while that of the other is sharply limited. The rays,
which at first are quite uniform in prominence, have been seen, at stages
a little later (Figs. 85, 82), to be differentiated in such a manner that
one side of the star is more conspicuous than the other. Whereas in the
earlier condition the central area appears spherical, in the more advanced
condition it is flattened in the direction of the line joining the halves of
MUSEUM OF COMPARATIVE ZOOLOGY. Peet
the amphiaster. The central portion of each aster thus becomes some-
what lenticular in form. Its outline is less convex on the face, which
looks toward the remaining aster of the pair. More or less in con-
formity with this change in the shape of the stellar “areas,” the asters
themselves are modified from the perfectly spherical appearance which
they at first present. The rays are no longer of the same length, nor
are they all uniformly tapering. At some distance from the centre is
disposed a more or less complete zone of much thicker and more con-
spicuous fibres (Figs. 85, 82). These are not thickened throughout their
whole extent, but are abruptly enlarged. The enlargements are con-
tinued for a distance equal to the breadth of the zone, when they are
as abruptly reduced to the ordinary dimensions. These zones are not
of uniform prominence on all sides of the aster, but in places gradually
fade away.
The central area of each stellate figure may remain for some time
homogeneous (Fig. 85, aa); at length there appear within it, however,
groups of highly refractive granules (Fig. 82), which, with the flattening
‘of the area, assume a corresponding distribution, so that when seen in
profile they have an irregular linear arrangement. When the stellate
figures have attained this complication of structure (Fig. 82), the pro-
nuclear bodies are no longer recognizable as distinct structures. All
that is left to indicate their previous existence are numerous dark gran-
ules irregularly arranged midway between the two asters, and, in a region
that is now traversed by stellar rays, a few very faint circular outlines
(pnl ?) of a size corresponding to that of the pronucleoli in the stage
just preceding. The indistinctness of these circular outlines prevents
that certainty which one feels in regard to the existence of the dark
granules, and this mistrust is increased by the appearances presented by
other eggs (Figs. 86-89), where there is found a trace of the nucleus of
the first cleavage sphere, but where there is no evidence of any contained
nucleolar bodies. Notwithstanding this apparent contradiction, I am
inclined to believe that occasionally the pronucleoli may in part persist
even after the disappearance of the outline of the pronucleus, and after
its substance has become so diffused as to be no longer readily distin-
guishable from the surrounding vitelline substance.
The dissolution of both these structures — the pronuclear membrane
and the pronucleoli— doubtless falls within a very limited extent of
time, and it may not be wrong to infer that in one instance the disap-
pearance of the one precedes, whereas in another case the disappearance of
the other first takes place. A trace of the nuclear substance has even been
228 . BULLETIN OF THE
found at a somewhat later period; at a time, namely, when the spindle
of the first cleavage sphere is fully formed (Figs. 88, 89), and possessed
of equatorial thickenings.
The remnants of the nuclear structure sustain such a topographical
relation to the forming amphiaster and spindle as to leave little doubt
that the latter take their origin nearer the centre of the vitellus than
the place occupied by the pronuclei, so that the substance of the pro-
nuclear bodies moves from its superficial position toward the centre in
contributing to the formation of the spindle. The opinion that such a
motion of nuclear substance as here suggested actually takes place, may
find support in the shape often presented by this nuclear remnant. It
seems to be elongated toward the amphiaster, and sometimes shows
(Fig. 87) a sort of filamentous structure, as though individual fibres of
substance were being drawn into the forming spindle. These nuclear
remnants are flattened in such a manner that they are seen edgewise
when one looks along the axis of the forming spindle. As a conse-
quence, they are more conspicuous when viewed in this position than
when seen en face. In the latter case the outline is much less regular, |
and in places may be quite indistinguishable ; especially is this the case
along the border directed toward the amphiaster. For this reason it
is not easy to satisfy one’s self as to the exact direction in which the
nuclear substance is tending. Seen edgewise, it is unequivocally directed
toward the axis of the spindle. But toward which part of the axis, —
toward the middle, or toward one or both of its apices? This can be
satisfactorily answered only by a study of the face view. Though not
so satisfactory as the former aspect, this view favors the belief that the
nuclear substance is being transferred toward the equatorial region of
the spindle.
The spindle is formed some time after the first appearance of the
stellate figures. It is only in an advanced stage of the metamorphosis
that the existence of such a structure, distinct from the general radia-
tion about the centres of the two asters, becomes evident. I have
seen very delicate and inconspicuous fibres stretching from star to
star outside the pronuclear structures at the early stage represented
in Fig. 85. These, however, are not distinguishable from the neigh-
boring rays of the asters, unléss it be by a somewhat greater length.
The centres of the stars lie deeper (farther from the animal pole)
than the adjacent surfaces of the pronuclei, so that if spindle fibres
are present, as I believe, they must lie external to the pronuclei.
Even in the later stage represented by Fig. 82 the limits of the spindle
MUSEUM OF COMPARATIVE ZOOLOGY. 229
are not satisfactorily indicated. In other cases, even before the entire
disappearance of the nuclear structure (Fig. 86), a portion of the rays
form a continuous, thick, spindle-shaped body, whose fibres converge to-
ward the centre of the asters. ‘These interstellate fibres, however, are
not traceable to the centres of the stars, but are lost in the margins of
the central “areas.” The limits of the spindle are much more clearly
indicated a little later, when equatorial thickenings appear. Occasion-
ally, however, the arrangement of the thickenings in the equator is very
irregular (Fig. 92). I believe, but cannot say with certainty, that
this indicates an early condition, and that it is followed by a more
regular arrangement. Usually the equatorial thickenings are so uni-
formly disposed that their combined effect is the same as though re-
sulting from a flat disk occupying exactly the equator of the spindle
(Fig. 89). The thickness of the latter is somewhat more than half its
length (Figs. 83, 89). An optical section corresponding to the equa-
torial plane (Figs. 84, 92) shows that the thickenings in the case of
this amphiaster, as in that of the archiamphiasters, are arranged in the
form of a ring, so that it may be inferred that the nuclear fibres are
themselves more numerous near the surface than at the axis of the
spindle.
The changes in the general outline of the vitellus, which have already
been noticed in speaking of the living egg, are preserved in those treated
with acid. The first change —a lengthening of the axis of the yolk
which is parallel to the spindle occurs at about the time the equa-
torial zone of thickenings is formed. This prolation of the yolk is quite
apparent, as in Fig. 89.
A comparison with views along the animal radius, however, shows that
this change of form is as much due to a flattening at the animal pole,
»and consequent shortening of the corresponding axis, as to a lengthen-
ing in the direction of the spindle. In such a view, either from the
animal or from the vegetative pole, the outline of the yolk may remain
circular, even when the spindle is completely formed (Fig. 83).
Up to this time the stellate figures have been constantly increasing
in size, though not uniformly on all sides. The rays are traceable for
the greatest distance in planes passing through the centres of the stars,
and parallel with the equator of the spindle. More than half the rays
of each aster are found on the distal sides of these planes. Each of the
asters is substantially hemispherical. The rays now stretch out to near
the periphery of the yolk, and approach each other along the equatorial
plane. The latter thus becomes apparent as neutral territory, where
230 BULLETIN OF THE
the forces inducing the stellar figures have not extended their influ-
ence, or serve to hold each other in check. It is along this plane that
the deepening fissure passes which ultimately separates the yolk into
two equal spheroids.
But while these changes in the form of the yolk are in progress,
the spindle undergoes modifications like those which transpire in the
maturation spindles. The equatorial zone of thickenings splits into
lateral halves, which migrate each toward the corresponding apex of the
spindle. Such, at least, is the inference to be drawn from the fact,
that, after the flattening and during the subsequent constriction of
the yolk, the equatorial zone is wanting, and in its stead two lateral
zones are found, which are farther from the equatorial plane the deeper
the constriction. That the migration of these thickenings is compara-
tively rapid may be inferred, I think, from an examination of Fig. 90;
the separation of the two lateral zones there exhibited having been ac-
complished between the beginning of the depression at the animal
pole and the appearance of a shallow furrow at the opposite side of
the yolk. When seen exactly edgewise, the lateral zones present a
linear arrangement of the thickenings parallel to the equatorial plane,
but a slight deviation in the direction of sight causes each lateral zone
to assume an oval outline, one edge of which appears, however, by
careful focusing, a little deeper than the other. This is represented in
the drawing by making the deeper half of the outline less distinct.
As the constriction advances from the animal pole, the interzonal fila-
ments (Kernjdden, Strasburger) which were left behind by the separating
lateral thickenings, are forced before it, and thus become bent so that
their convexities are directed toward the vegetative pole. This bend
retains for some time the nature of a full uniform curve on the convex
side, but on the indented side it soon assumes a more angular ap-
pearance (Fig. 93). The interzonal filaments thus continue to be carried
forward by the advancing depression of the yolk without surrendering
their continuity. In this manner they become lengthened, inasmuch as
the position of their extremities remains comparatively uninfluenced by
this change. They thus form a sort of V-shaped figure, whose free ends
terminate in the lateral zones of spindle-fibre thickenings. In all this
process the interzonal filaments appear to play an entirely passive réle.
Meantime the lateral zones have assumed the nature of nuclear vacu-
oles containing each a number of nucleolar bodies. Whether this has
transpired by the accumulation of nuclear sap in the region of the
thickenings, now converted into nucleolar bodies, or has resulted from a
MUSEUM OF COMPARATIVE ZOOLOGY. Zak
confluence of the thickenings in which new nucleolar structures have
arisen, 1 am unable to determine. ‘The fact that no cases of entirely
homogeneous nuclei have come under observation, does not seem favor-
able to the latter hypothesis, and yet the same method doubtless
prevails here as in the formation of the female pronucleus. Treat-
ment -with acetic acid has invariably resulted in a shrivelled appear-
ance of the nuclei. With the deepening of the constriction from the
animal pole, the two nuclei assume a lengthened form, and take posi-
tions such that theirs long axes correspond approximately with the
trend of the interzonal filaments. Toward the close of the constriction
(Fig. 91) each of the nuclei has attained a length of a quarter to a
third the diameter (ca. 35.) of the resulting cleavage spheres. Its
breadth is not more than half its length. It is somewhat more convex
on the face which looks toward the animal pole. Double contour lines
are more manifest with increasing size. Both the number and mag-
nitude of the nucleolar bodies increase. They now number twenty
or thirty. They vary in size from 3p or 4 to less than 1p, and are
nearly spherical.
When the constriction has advanced from the animal pole to the
centre of the yolk, the interzonal filaments are most conspicuous exactly
opposite the constriction, where they appear somewhat thickened. These
thickenings, however, are never abrupt, but taper gradually on both
sides, till, in the vicinity of the nuclei, the filaments become quite faint.
As the constriction advances further, this indistinctness affects more and
more the terminal portions, till at length only very short, rapidly tapering
threads are seen. These, however, persist for some time; they may
even be discovered near the surface of the yolk after the two spheres
have become detached from each other, and have entered upon other
phases of relationship. These thickenings are doubtless equivalent to
the so-called “cell-plate” of Strasburger (Zellplatte). The last point of
union between the halves of the first segmentation sphere is marked by
this remnant of the interzonal filaments ; it is they which are last to
yield to the force that divides this first cell into two.
There remains still another point to be mentioned in connection with
the phenomena presented by eggs hardened during the process of cleav-
age. Itoften happens that this treatment causes a thin, superficial layer
of the yolk to become separated from the rest of the vitellus on that
side where the constriction is farthest advanced (Figs. 90, 93). This ap-
pears as a homogeneous structure, less than 1p in thickness. The
inner surface is less sharply marked than the outer, and from the fact
232 BULLETIN OF THE a
.
that it is only incompletely differentiated from the underlying granular |
protoplasm it is found in places to have portions of the latter clinging —
_ to its inner face. From this I can hardly conclude otherwise than that
a differentiation has already begun in the superficial portion of the yolk,
which is the first step toward the formation of a cell membrane, and that
this differentiation is proportional to the advance of the cleavage. It
is unquestionably owing to the action of the acid that this layer be-
comes detached from the vitellus ; but it seems to me unnatural to con-
clude that the homogeneous layer has itself been produced by the action
of the reagent.
B. BIBLIOGRAPHY.
I. Limax.
The embryology of Limax has been studied by a number of natu-
ralists. The most of the papers on this subject, however, were written
many years ago; indeed, no extensive contribution to the embryology
of Limax has appeared for the last quarter of a century. The phe-
nomena which are considered in the present paper were in many cases
either briefly touched upon, or fell altogether outside the province of the
authors’ investigations. Of the latter class, and consequently of less
immediate concern at present, are the papers of J. L. M. Laurent (37,
37°, 37°, and 38°); P. Laurent (42); Dujardin (37) ; Schmidt (SI) ; ;
Gegenbaur (’52) ; and Lankester ("74 and "75*).*
1. Egg Envelopes, ete.
The composition of the egg at the time of extrusion has been studied
by several writers, whose conclusions, though not difficult to interpret,
are somewhat at variance.
The earlier descriptions date from a time when the process of segmen-
tation was as yet unknown in Mollusks. It would be unreasonable to
expect from them valuable observations on many of its structural
features. |
Turpin’s (32, p. 435) description is substantially as follows. The
eggs of Limax flavus (Fig. 9) are oblong, terminated at each end by a sort.
of umbilical chord ; they are transparent, bluish or grayish, soft and gelati-
nous. The eggs of the Limaces are composed, like those of Helices, of
* The numbers in Egyptian type following an author’s name are abbreviations
for the year of publication, —e. g. ’8'7,’37°, ’37°, all appeared in 1837, — and serve
at the same time to refer the reader to the alphabetical list of authors quoted.
a
MUSEUM OF COMPARATIVE ZOOLOGY. 233
four parts: two envelopes, an albuminous liquid, and a cicatricula. The
exterior mucous envelope, which is quite thick and resistant, is distin-
guished by a sort of loose network composed of very delicate fibres.
The interior envelope, of extreme thinness, hyaline, and likewise fur-
nished with a fibrous network, contains the albuminous liquor and the
cicatricula. The eggs of Limax rufus appear entirely like those of
Limax flavus.
The figure given by Turpin is not such as to aid materially in under-
standing the structure. His exterior envelope includes both the exter-
nal stratified and the homogeneous layers, while his internal envelope
is the membrana albuminis, whose wrinkles were probably mistaken for a
fibrous network. The cicatricula is the yolk..
The description given three years later by J. L. M. Laurent of the
egos of Limax flavus and of those of ‘“ Limace rouge,” differs from that
of Turpin in only two or three points.* Passing from without inward,
Laurent (’35°, p. 249) found in succession : —
1. A mucoso-corneous shell, evidently formed of concentric layers.
2. An internal membrane.
3. Two albuminous layers, the more liquid enveloping the denser
one.
4, A very small vitellus, whose color, a slightly yellowish gray, varies
with the incidence of the light.
No other author, so far as I know, has observed any differentiation of
the albumen into a denser and a more fluid portion. His “ internal
membrane” doubtless corresponds to the memb. albuminis, and his
“shell,” the concentric layers of which are first mentioned by this
author, embraces, like that of Turpin, the homogeneous as well as the
stratified portions. In a subsequent paper, accompanied by a plate, this
author (38, pp. 155, 333, and Pl. 3) states that between the corne-
ous shell and the internal membrane there is a clear space, which is
traversed by fibrillee (which in his Fig. 1 show a reticulated arrange-
ment) joining these two structures. A transparent, watery fluid may
accumulate in this clear space. It probably corresponds with the
viscid, unstratified shell layer of later observers. It is possible that
Turpin saw some such network of fibrillz, and hence ascribed to the
whole of the outer thick envelope this structure. I do not find it men-
tioned by subsequent observers, nor have I seen any such peculiarity
myself.
* The eggs of L. flavus are united in a chaplet ; those of “ Limace rouge” are
smaller and isolated.
234 BULLETIN OF THE
It is possible that Laurent had observed the so-called chalaza at the
time (1835) his first article was published ; but it was subsequent to
the appearance of a paper by Van Beneden and Windischmann, — in
fact after that paper was already known to him, —that he speaks (38,
p. 134, foot-note), for the first time, of a “filament tortillé qui existe
constamment dans tous les ceufs de limace.” This is described more
at length on page 146 of the last-mentioned paper.
Although Dumortier (37) states in his memoir on the development
of Mollusks that he has studied the eggs of Limax, his results are all
drawn from the study of Lymnzeus ovalis.
In the same year (1838) that the last-mentioned paper of Laurent
appeared, Van Beneden and Windischmann (’38) wrote of Limax
agrestis as follows: ‘As regards the composition of the egg, we have
found almost nothing which does not accord with the observations
of M. Laurent. Nevertheless, we have established the presence of a
‘cordon filamenteux’ which becomes especially visible at a certain
epoch of development, and which appears to us to have an evident
analogy with the chalaza of the eggs of birds. This same cordon has
already been pointed out, however, in the eggs of Helix pomatia.” |
In their final paper (41, p. 6 [p. 20, Ztudes], and ’41°*, pp. 178, 179),
published in 1841, these authors announced the following as the com-
position of the egg, from within outwards: Ist, a vitellus; 2d, a great
quantity of albumen holding in suspension the “filament entortille” |
(previously called “cordon filamenteux”); 3d, a delicate, transparent
membrane covering the albumen; 4th, a slight layer of liquid; 5th, a
quite thick exterior membrane composed of numerous layers. The points
of correspondence with the descriptions of Turpin and Laurent are ap-
parent. The clear space of the latter author is the liquid layer of Van ~
Beneden and Windischmann. The structure called “ filament entortillé”
was at first (1838) regarded by Van Beneden and Windischmann as
homologous with the chalaza of birds’ eggs, but, from the variations oc-
curring in different eggs, they subsequently concluded that it was a torn
membrane which at first surrounded the vitellus, and that consequently
it really appertained to the vitelline membrane. The latter view has_
been sufficiently refuted by Warneck (’50, p. 107).
The description of the egg by the last-mentioned observer (pp. 105-
111) differs in some points from that of his predecessors. The albumen
is invested by two membranes, — membrana albuminis secundaria sew
interna, and membr. alb. primaria seu externa. The former is easily
thrown into folds by compression ; the latter is much thicker than the
MUSEUM OF COMPARATIVE ZOOLOGY. 235
former ; both are structureless. External to the latter is a layer of
viscid mucus (Schleim), which fills all the space between the external
membrane and the stratified, elastic shell. In approaching the deeper
_ portions of the layer this mucous substance increases in consistency.
I have been unable to discover the membrana externa, and believe that
the structure so named by Warneck may be only a somewhat denser
portion of the mucous layer, which does not always differ enough in re-
fractive power from the remaining portions of the mucus to make it
distinguishable.
Warneck (’50, p. 108) says that crystals of lime carbonate are found
on the outer surface of the outer shell, insome places united into a
druse; and subsequently Gegenbaur (52, p. 372), evidently without
knowledge of Warneck’s paper, reported that one very frequently sees
in the middle strata of the layers of the outer shell deposits of the same
substance in the form of dark round concretions, which also often
assume a crystalline structure. I have seen nothing of the kind.
2. The Yolk and tts Changes.
The authors who have studied the early condition and changes of the
yolk of Limax are J. L. M. Laurent, Van Beneden and Windischmann,
Warneck, and Gegenbaur.
Very little is to be learned from Laurent (’35°, and ’38, p. 136),
further than that he believed the vitellus might vary considerably in
form, and that it appeared to embrace a variable number (15-20) of
large globules containing smaller ones, — views which show clearly that
he is more likely to have had under observation segmenting eggs than
such as had not reached the cleavage stage.* In view of this fact, not
much importance attaches to his statements when he informs us, that a
central whitish spot, situated more or less closely to the circumference,
is visible by reflected light, and may be due to reflection of the light
alone (!) ; that he has never succeeded in recognizing the least indication
of a cicatricula produced by the liquid of the germinative vesicle ; or
that he thinks there is a vitelline membrane.
From what has already been said of the view entertained by Van
Beneden and Windischmann (’41*, pp. 179-181, Taf. 7) as to the
nature of the “ filament entortillé,” it will be clear that they inclined
to the belief that the freshly deposited egg was without a vitelline mem-
brane. All the eggs observed by Van Beneden and Windischmann had
* The process of segmentation in Mollusks, as is well known, was first announced
by Sars (’37, p. 402), in 1837.
236 BULLETIN OF THE
been deposited for a longer or shorter time. In keeping with the then
prevailing opinion of the total disappearance of the germinative vesicle,
they report not being able to find a trace of it at the centre of the
yolk. ‘The first change observed was the appearance of a transparent
vesicle, which seemed to escape from the midst of the yolk, and was
soon followed by a second. These vesicles (polar globules) are never — |
wanting, and always escape from the same side of the yolk. After their
escape, the space which they have traversed appears clearer (deep aster ?)
than the rest of the vitellus (sufficient cause for them to institute
-a@ comparison with the vase-shaped portion of the white yolk in the
fowl’s egg). The vesicles contain granules some moments after their
escape ; they take no part in the formation of the embryo, but are sub-
sequently absorbed in the albumen. The observers are unable to say
whether these vesicles have any analogy with the germinative vesi-
cle, but think it in no way astonishing that the latter should escape
from the yolk, if the vitelline membrane has suffered the change above
alluded to, although the vesicle would in that event cease to have the
important (germinative) 76le attributed to it in higher animals.
What is said concerning the first segmentation becomes intelligible
only by comparing with the figures, and apparently rests on a miscon-
ception of the order of events. It is stated (p. 181) that, after the escape
of the two vesicles, the middle of the vitellus becomes clearer, and is
divided into two equal portions, and that subsequently a furrow makes
its appearance at the side opposite that where the (polar) vesicles es-
caped. An examination of Fig. 5 (Taf. 7), which is described (p. 194)
as representing the stage in which the yolk has become clearer in
the centre, shows conclusively, to one who has seen the object itself,
that the clearness in question is due to a lense-shaped accumulation
of a transparent fluid between the cleavage spheres,* and that con-
sequently the figure represents a stage after the first cleavage. I am
unable to explain how it happens that the cleavage furrow should be
considered as first appearing at the side opposite that where the polar
vesicles arise (see Fig. 7). That the process was not very carefully ob-
served is moreover sufficiently demonstrated by this Figure 7, for it un-
questionably represents an egg after the first segmentation, and after
the accumulation of the lenticular mass of fluid above alluded to.
Warneck (’50, pp. 102, 103, 105, 114) thinks that the yolk in the
eggs of Lymnzeus and Limax has no special envelope, but is simply
* This interesting phenomenon has been in most points already well described by
Warneck, and has been seen in other than molluscan eggs.
MUSEUM .OF COMPARATIVE ZOOLOGY. 237
clothed in a layer of soluble protoplasm (Schleim) which takes the place
of a membrane. It possesses an envelope (/iil/e), it is true, but it is
not membranous, —it is simply one of thickened protoplasm. For
this reason the author cannot agree with those who do not admit the
existence of any envelope.
The observations of Warneck on the early changes of the egg in
Lymneeus and Limax were far more extensive and accurate than those
of his predecessors ; they were, in fact, in advance of most of the con-
temporary studies in other branches of embryology, and came near
anticipating some of the more important discoveries of the present
decade. His paper (1850) marks approximately the beginning of a
reversion of ideas as to the total disappearance of the Purkinjean
vesicle which had been dominant since its discovery in 1825; and, if I
have not mistaken his meaning, Warneck may fairly be reckoned among
the first who entertained doubts as to a complete dissolution of this
structure.
It must be admitted, however, that the reputation of Johannes
Miiller was the sufficient cause for the more general reception of new
views on this point in embryology. Although Warneck’s paper ante-
dates by two years that of the latter author, there can be little question
that the influence of his writing has been inconsiderable when compared
with that of Miiller.*
According to Warneck (’50, pp. 114, 115) one discovers within the
yolk-mass of the impregnated egg a clear spot, which is due to a cavity
filled with an albuminous fluid as clear as water, and containing no
elementary corpuscles, such as occupy the yolk. This clear spot occu-
pies exactly the place of the Purkinjean vesicle. No distinct contour is
observable, the transparency of the spot diminishing toward the periphery,
so that it gradually merges into the yolk-mass. Its position is central.
Although not thus sharply formulated, I think there can be no doubt
that Warneck believed the “clear spot” to be the Purkinjean vesicle
metamorphosed by the disappearance of its membrane and its numer-
ous germinative dots (p. 177).
* Among others, Hermann Fol has recently called attention to this paper by War-
neck, whose work he estimates very highly. While one cannot fail to admire the
generous spirit which prompts this opinion of the merit of Warneck, it is much more
difficult to subscribe to the interpretation which Fol puts upon certain portions of his
paper.
Brandt ('7'7°, pp. 593, 594) has made use of the studies of Warneck to corrobo-
tate his own observations on the ameboid nature of the germinative vesicle, in a
manner which appears to me unjustifiable, as will presently be shown.
238 BULLETIN OF THE
The changes affecting this clear spot are briefly as follows (pp. 116-
118). The spot, which at first appears quite round from whichever side
viewed, becomes lengthened in the direction of a diameter, and assumes
successively the forms of a biscuit (Semme/) and of a figure 8, and finally
becomes fully separated (i. e. differentiated) from the remaining yolk-
mass.* This process is one of segmentation or division. The constricted
“spot” migrates toward a definite point of the periphery. The end
which the contents of the spot approach, becomes considerably en-
larged, so that the clear spot assumes the form of a blunt rounded
cone.t If the egg of Lymneus vulgaris arrived at this stage be
crushed, it will be found that the spot really consists of two globular
parts surrounded by a transparent protoplasmic substance (Schlevm)
which considerably increases the size of the spot. The very thin enve-
lope (Mille) of the spheres contains a transparent albuminous fluid,
of the same nature as the surrounding protoplasm (Schleem). In the
case of Limax agrestis the phenomena are substantially the same. The
two spheres become readily distinguishable, especially when one of them
moves outward (through the yolk).#
* *¢Der Anfangs vollkommen runde Fleck verlingert sich in der Richtung des einen
Durchmessers, nimmt durauf eine biscuitanhliche Form an, dann die Form einer 8 —
und zuletzt trennt er sich ganz von der iibrigen Dottermasse.”
Another rendering of this passage would be, ‘‘and finally becomes completely
eliminated from the remaining yolk-mass.”’ There is also one other passage which
might possibly support this view. I shall presently quote and endeavor to
explain the second passage. The objection to accepting any interpretation which
admits that the spot is eliminated, is the positive denial of it subsequently made
by Warneck.
+ ‘*Das Ende, welchem sich der Inhalt des Fleckes nihert, vergréssert sich
bedeutend, so dass der helle Fleck die Gestalt eines stumpfen, abgerundeten Kegels
annimmt.”
t As the passage last alluded to (Warneck, 750, p. 118) seems to have been the
cause of some misunderstanding, I will give it in full: ‘‘ Es bilden sich also im
hellen Flecke bei Limax auch zwei Kugeln, welche besonders deutlich unterschieden
werden kénnen, wenn die eine von den Kugeln nach aussen tritt, wie es gleich
beschrieben werden wird.”
The interpretation of the author’s statement turns on the meaning of ‘‘nach aus-
sen tritt.”” I understand by it the same as would have been expressed by say-
ing “nach aussen — nach der Peripherie zu — tritt.” Had it been the intention of
the author to say that one of the spheres was eliminated, he would have used
‘‘heraustreten.”
The difficulty of understanding what is meant results from the addition of the
clause, ‘wie es gleich beschrieben werden wird.” There is nothing in the subse-
quent description to which this allusion can refer, except the formation of two polar
globules. It is probably on account of this that Warneck has been understood to
MUSEUM OF COMPARATIVE ZOOLOGY. 239
The description thus far evidently relates to the formation and migra-
tion of the structure called in the present paper the jirst archiamphi-
aster, and to the method of its production from the clear spot which
succeeded the Purkinjean vesicle. Although revealing none of the
finer structural changes which have recently been brought to light, this
description leaves no doubt as to the nature of the object, nor the sub-
stantial accuracy,of the observations. The same cannot, however, be
said regarding some of Warneck’s subsequent statements. One does
not, at least, feel the same certainty that the author has before him this
archiamphiaster phase of development when he says (p. 119) that the
difference between Limax and Lymneeus consists only in this, that each
sphere in the case of the latter possesses a thick envelope with two dis-
tinct contours. This statement does not agree with that already cited,
declaring the spheres to have a thin envelope. The discrepancy is
probably due to Warneck’s having confused the asters with pronuclei,
in which event the case of spheres with double contour must have been
such as is really found only at a later period, viz. after the formation of
the polar globules. It seems unreasonable that so accurate an observer
should have made such a mistake, and yet I do not see any other possi-
ble explanation. It would be entirely unreasonable to suppose that the
archiamphiaster in Lymnezeus possessed double contour lines, even if the
convincing studies of Biitschli on this genus were wanting. What is
said relative to the vesicles found in these nuclear spheres may well
be referred to the pronucleoli.
In Warneck’s opinion (pp. 121, 122) these two nuclear spheres remain
quite passive during the formation of the polar globules, which takes
place from the pole of the yolk toward which the spheres have migrated.
This process is described at some length.
Fol, it is true, finds authority in Warneck for saying that one of these
nuclear spheres escapes under the form of globules, — the excretory (or
direction) corpuscles.* The only passages allowing such an interpre-
tation are the ones already quoted, but the subsequent statements of
Warneck are so entirely unequivocal that I cannot hesitate in believing
his conception to have been quite unlike that which Fol ascribes to him.
Warneck says (p. 120) that there appears between the outer rim (i. e.
say that the polar globules are produced by the elimination of one of the nuclear
spheres. On the other hand, he states, in the most positive manner, that the polar
globules have nothing to do with these nuclear spheres. (See below.)
* “Cette tache se divise en deux moitiés, dont l’une reste au centre du vitellus,
tandis que l’autre arrive 4 la surface, et sort sous forme de globules : les corpuscles
excrétés (ou de direction).” (Fol, °75%, p. 22.) Compare also Fol, op. cit., p. 26.
240 BULLETIN OF THE
the base) of the conical spot and the envelope of the yolk a clear cres-
cent-shaped place, which can be plainly distiguished from the clear spot
and the remaining yolk-mass. A little further on, he says the crescent-
shaped space shows quite clearly that the nuclei do not in the least take
part in the formation of the outer vesicles (polar globules).*
If this understanding of Warneck be the right one,f it will be seen
that his observations on the archiamphiaster are not only very in-
complete compared with recent studies, but that they are radically at
fault in making this structure and the polar globules independent of each
other. It might at first seem somewhat strange that no evidence of
radiate structure should have come under his eyes, inasmuch as he cer-
tainly made use of acetic acid; but the probable use of a concentrated
acid, and the absence of any staining process, — which latter is really
of very great additional value,— are doubtless sufficient to explain this
oversight.
First there appears, then, according to Warneck, a clear crescent-
shaped place between the outer rim of the conical spot and the pro-
toplasmic envelope of the yolk, which can be clearly distinguished
from the clear spot and the remaining yolk. This is erroneously con-
sidered by Warneck as identical with a most interesting and peculiar
* The words of Warneck (pp. 121, 122) are as follows: ‘‘ Der sichelformige Raum,
welcher die urspriingliche Erhabenheit [of the polar globule] von dem hellen Flecke
trennt (d. h. den beiden Kernen mit ihrer durchsichtigen, eiweissartigen Hiille), zeigt
ganz deutlich, dass die Kerne nicht im Mindesten an der Bildung der dusseren
Blaschen Theil nehmen. Daher muss ich mich durchaus gegen die Ansicht erkla-
ren, nach welcher die Blaschen aus dem Centrum der Dottermasse entstehen sollen,
oder, was einerli ist, dass diese Blaschen als vesicula Purkinji oder als Ueberbleibsel
derselben zu betrachten seien. Ich bin ganz tiberzeugt davon und meine Abbildungen
zeigen dieses ganz deutlich, dass die Hiille der Blaschen urspriinglich mit der Dotter-
hiille ganz gleichbedeutend, und der Inhalt derselben aus dem sichelformigen Raume
entlehnt sei.”
t P. S. —Since writing the above, I have chanced upon Biitschli’s (776, pp. 242,
243) interpretation of Warneck, which I had overlooked. Biitschli’s conclusion
is substantially the same as that to which I have arrived, and he also finds him-
self compelled to pronounce Fol’s interpretation wrong, without, as it seems,
having discovered the two passages which make the chance of such a mistake possi-
ble. It seems a little strange, in view of this criticism by Biitschli, that Fol still
maintains the same estimate of Warneck’s meaning touching the relation of the ar-
chiamphiaster to the polar globules. Fol (°79, p. 149) writes as follows: “ Le cone
transparent prend une forme plus évasée et sa partie superficielle donne naissance,
par une sorte de bourgeonnement, d un globule polaire, puis 4 un second, et rarement
encore A un troisitme.” Perhaps the passage in Biitschli’s work has escaped the at- |
tention of Fol, as it at first did mine.
we
MUSEUM OF COMPARATIVE ZOOLOGY. 241
phenomenon which reappears with each segmentation ; viz. the accumu-
lation of a transparent fluid secretion, which becomes periodically evacu-
ated into the surrounding albumen (compare pp. 131-136, J. ¢.).
In this stage there are produced out of this crescent two vesicles
whose emergence begins by the protrusion of a small elevation (kleine
Erhabenheit) through the protoplasmic envelope of the yolk. The
elevation increases, assumes the form of the segment of a sphere, then
that of a hemisphere, which gradually becomes a complete sphere rest-
ing on a rather stout pedicel. By a constriction of the latter, the
sphere appears as a free vesicle. The statement that the second appears
gleich after the formation of the first, cannot be taken as exactly rep-
resenting the facts. The first globule is larger than the second, and,
while the former contains in its clear albuminous fluid small elementary
granules, the latter contains a nucleus and nucleolus. Warneck also
observed, though very rarely, a third vesicle. The globules do not
take part in the formation of the embryo, but continue to exist in a
collapsed condition till the young slug escapes from the egg-shell.
For Warneck these vesicles have not the great importance implied in
the name “ Richtungsblaschen.” The coincidence of the place of their
appearance and that of the first traces of segmentation does not establish
the dependence of the latter on the former. The views of Bischoff, Kol-
liker, and Reichert, in referring these vesicles to the germinative vesicle,
are especially denied, as far as relates to the snails; and, as we have
already seen (p. 240), their connection with the “clear spot ” is denied
with equal emphasis ; from all which I believe it clearly follows, as stated
above, that Warneck entertained the opinion that a genetic connection
did exist between the Purkinjean vesicle and the “clear spot.” *
Warneck’s interpretation of the physiological signification of the polar
globules hinges on the supposed identity of their formation and detach-
ment with the later phenomena of the elimination of a clear liquid. Of
the vesicles themselves, he says, they in all probability remove from the
yolk an albuminous fluid (p. 123). Of the later phenomenon he says
(p. 134), “Die untauglichen Stoffen werden auch bei dieser Art der
Thatigkeit durch Exosmose entfernt.”
From a comparison of the text (p. 125) with the descriptions of the
figures (pp. 180, 181) we learn that the elimination of the polar globules
* P.S. — Again in this point I cannot agree with Fol (’79, p. 145) when
he cites Warneck in the following connection : ‘‘ Dans l’embranchement des Mol-
lusques, la disparition du noyau de l’ovule a été reconnue par de nombreux observa-
wears. .... Je citerai les travaux .... de Warneck pour Limneus et Limax.”
VOL. VI.—No. 12. 16
242 BULLETIN OF THE
is followed by important changes in the yolk. The crescent-shaped
space disappears. The “clear spot” passes from the conical to an oval
form, then becomes figure-eight-shaped, and finally appears as two dis-
tinct nuclei, which are distinguishable from the earlier condition by
reason of the sharp contour of the walls, and the presence of a large
nucleolus in addition to less prominent vesicles. These nuclei have an
eccentric position ; they lie nearer the point whence the polar globules
were detached.
There can be no question about these nuclei being really the male
and female pronuclei. I have not, however, been able to discover in
either of them in the case of Limax campestris a single nucleolus of
greater size and refractive power than the other contained bodies. The
contour of these nuclei (pronuclei), says Warneck, grows indistinct, their
envelopes are dissolved, and the contents of the two form a single mass,
which, before the division of the yolk, becomes oval, and then biscuit-
shaped, with the long axis at right angles to the position previously (in
the conical clear spot) occupied (nucleus of first cleavage sphere 2).
What Warneck has said of the cleavage of the yolk, as observed in
the living egg, is of less immediate interest, and from its substantial
agreement with the description given in the first part of this paper may
be passed with a few words upon a single point. Warneck says (p. 128)
that the plane of the first cleavage furrow is not perpendicular to the
long axis of the yolk, but cuts it at an angle of almost 45°. I have some-
times seen such an obliquity in the course of the furrow, though never
so great an angle, nor do I think it can be true for anything like a
majority of cases with Limax campestris.
I return to his account of the clear nuclear spot. With the length-
ening of the yolk, and its constriction, the spot diminishes to one fourth
its former dimensions, and is only visible with difficulty, especially in
the case of Lymneus.*
There can be no doubt, he very rightly affirms, about the dissolution
of the nuclear membrane and the nucleoli. This, and the failure of the
nuclear substance to curdle when exposed to water, lead him to the con-
viction that this clear spot has again altered its chemical properties, and
* The somewhat incongruous statement that, for Lymneus, this obscurity arises,
as he thinks, from the fact ‘‘that the contents of the nucleus mingle with the re-
maining yolk-mass, and that the spot (Fleck) withdraws itself to the centre of the
yolk at the formation of the dorsal [i. e. at the animal pole] furrow,” could not have
outweighed in his own mind the direct observations of a division of the spot in the
case of Limax.
MUSEUM OF COMPARATIVE ZOOLOGY. 243
that this must be the cause of its further metamorphoses. Finally,
during the division of the yolk, the clear spot becomes fully divided
into two parts, each with a trail, like the tail of a comet, stretching
away toward the last point of contact. The trails soon disappear, and
the spots gradually assume the globular form, though not yet capable
of being isolated from the yolk, from which he concludes the nucleus has
not yet a distinct membrane.
Accompanying the subsequent approach and mutual flattening of the
cleavage spheres* the nuclei acquire a membrane. That Warneck had
observed very closely the formation of the new nuclei must be evident,
I think, from the following passage (p. 138): “Im Anfange .... sind
sie [die Kerne] noch sehr klein (noch kleiner sogar, als diejenige helle
Masse, welche in jede Kugel sich absondert) und fast glaube ich, dass
nicht die ganze Masse unmittelbar in jede Kugel [jeden Kern? ] itiber-
geht, sondern nur ein gewisser Theil derselben wird Anfangs, gleich
einem Centrum, von einer Hiille umgeben und vergrossert sich dann auf
Rechnung der sie umgebenden Masse.”
Gegenbaur (51, pp. 373, 374) has only incidentally touched upon
some of the questions which interest us, his main purpose being the
investigation of the genesis of the organs and their tissues. The ab-
sence of a cell membrane, owing to the essential importance at that
time attached to this structure, seems to have caused him to entertain
a less just conception of the cell nature of the cleavage spheres than
was held by Warneck ; for he remarks that only a negative result was
obtainable in regard to the question of the cell nature of these spheres,
imasmuch as he was in no way able to demonstrate a membrane, and
therefore concludes that these spheres are to be considered as in the
process of being generated into cells, — “‘als angelegte Zellen,” — which
only attain their formation into genuine cells after oft-repeated division.
The so-called ‘“ Richtungsblischen” arises through the elimination
(Ausscheidung) of a little drop of yolk substance, which often contains
various globules of fat, and often remains a long time in the vicinity of
the yolk without acquiring any further relation to the embryo except that
* Of the phenomena which are observable during or immediately subsequent to
this flattening, already very well described by Warneck, I will limit myself here to
the statement that in Limax campestris the elimination of the secreted fluid takes
place at the animal pole.
I-would also say concerning a subsequent phase of segmentation, that in L. cam-
pestris the stage consisting of 8 cleavage spheres is not followed by one of 12, but
both large and small spheres divide at the same time, so that the stage of 16 spheres
follows directly that of 8.
244 BULLETIN OF THE
it always arises from that part of the yolk where the constriction sub-
sequently appears. The statement that “Grosse sowie Anzahl ist sehr
differirend,” can only have been the result of a superficial study of these
bodies.
P. S. — Two papers on early stages in the embryology of Limax and
Helix respectively, one by Mayzel and the other by Pérez, will be con-
sidered in an Appendix.
II. Revirw oF Maturation, FECUNDATION, AND CELL-DrvisIon.
1. Cell-Division.
The significance of the now well-established cell theory is hardly
more far-reaching than is that of its legitimate offspring : the discovery,
on the one hand, of the substantial identity of cell-diviscon, whether in
the animal or the vegetable kingdom, whether at the beginning or at the
close of that cycle of events which makes up what we call the life of the
individual ; and, on the other hand, the growing conviction that fecunda-
tion is the reunion of forces which have suffered a complementary differ-
entiation in cells whose corresponding parts become directly commingled
in this act.
As the influence of the cell theory on investigations for the past forty
years can hardly be overestimated, so we may confidently look forward
for no mean outcome from the impetus imparted to biological research
by these more recent achievements. The influence of studies on cell
phenomena culminating in such broad generalizations, if less signifi-
cant to the popular mind than evidences of a process of evolution drawn
from the structure and habits of adult beings, is none the less securely
intrenching the belief in the consanguinity of all living things.
Of all the phenomena connected with cell-division, that which may be
designated as the metamorphosis of the nucleus has recently received
most attention. It is that which has remained almost up to the present
time superficially observed, not at all understood, and therefore the
cause of many conflicting statements. Some portions even of the more
obscure changes- which take place within the cell during the nuclear
metamorphosis were long ago seen, though hardly comprehended.
These observations were for the most part limited to the changed ap-
pearance of the protoplasm surrounding ‘the nucleus, —the stellate
figures, — and were made on one or the other of the two cellular ele-
ments of sexual reproduction. Previous, then, to the consideration
of the metamorphosis of the nucleus, the observations on the stellate
MUSEUM OF COMPARATIVE ZOOLOGY. 245
figures made prior to the time (1873) when they were shown to be in-
timately connected with the nuclear changes will be historically reviewed.
In order to study the changes which take place in the nucleus during
cell-division, it will also be desirable to review late studies and opinions
onthe nature of the quiescent nucleus, — if we may speak of an appar-
ently less active condition as a quiescent state. This will necessitate a
second digression, from the main topic, now under consideration.
a. ASTERS.
Stellate arrangements of the protoplasm surrounding the nucleus were ob-
served long ago, but it is very questionable if many of these earlier observations
were really made on the stellate figures which accompany cell-division. Es-
pecially doubtful are those descriptions in which a distinct nuclear structure is
made the centre of an extensive radiation in the protoplasm. For the fully
formed, conspicuous nucleus does not in most cases correspond to the stage
in which the radial arrangement is prominent. In fact, with the completion
of the nucleus, the radiate structure usually vanishes altogether. The repre-
sentation of rays about a nucleus is not enough, then, to warrant the conclusion
that an author has observed the astral figures which accompany division. To
accept such as sufficient evidence is to ignore an almost constant relation of the
astral centre to the nucleus.
One of the earliest and most striking cases of such a radial phenomenon is
that described and figured by Carus (32, pp. 44, 45, Taf. II. Figs. 3, 10, 11).
It is true Carus regards, though erroneously, the embryos (Unio) figured as
presenting abnormal conditions resulting from death, yet the nucleus and the
radial structure of the surrounding protoplasm are so clearly shown that at first
one would not hesitate to pronounce his figures to be those of veritable asters.
So strong as the resemblance is, it must, however, be admitted that it is at
best only a resemblance, and not a true aster. The latter does not exist when
the nuclei present the appearance reproduced in Carus’s figures. Flemming
does not hesitate, after a study of the same objects, to declare the radiation in
this case to be purely the result of a play of fancy.
The figures accompanying the work of GruBE on Clepsine (44, Taf. IIT.
Figs. 11, 12) would lead one to suspect that he might have seen the radial ar-
rangement of the protoplasm in the periphery of the nuclei, his “ Wandungs-
kugeln”; but Ido not find that he makes any mention of it in the text, and
am by no means sure that the radiate lines may not be due to something
entirely different, possibly to fissures caused by excessive or unequal hardening
of the eggs. At least, his figures do not present as acceptable evidence that
such phenomena were seen as do those which DERBES (47, Pl. V. Figs. 4, 6)
executed three years later in giving the embryology of the urchin (Echinus es-
culentus). Derbés’s first-mentioned figure is that of the egg after the disappear-
ance of the germinative vesicle,* but before the first segmentation. From the
* Derbées, it is true, did not regard his “sphére moyenne” as a germinative vesicle.
ad
246 BULLETIN OF THE
central position of the nuclear structure it is to be inferred that it is either the
female pronucleus, or, more probably, the primary segmentation-nucleus. As
no description of it is given, it is not possible to say with certainty which of
these structures it represents. The author says (p. 90, op. cit.) that after the
yolk divides the first time he has seen that each of the resulting segments con-
tains a small vesicle, and each of the vesicles is the centre of a shghtly confused
radiation. At the next subsequent segmentation he did not discover the vesi-
cle, but only the radiation around a more or less centrally situated point, and
in subsequent segmentations even this radiation was no longer perceptible.
Even in the case of the divided yolk, there is no evidence that Derbes saw an
amphiaster, or any part of the spindle.
In the same year (1847) similar phenomena were observed in the “ Brut-
zellen,”’ from which are produced the male elements of reproduction, — the
spermatozoa. REICHERT (’47, pp. 120, 121, Taf. V1. Figs. 1, 23, 24) was, so far
as I know, the first to discover this peculiarity of the sperm-cells, which he
describes in the case of a Nematode, Ascaris acuminata. After the division of
the parent cell into two, four, or more sperm-cells, each of the latter presents
a very peculiar and elegant radiate appearance in its central granular portion,
which constitutes the principal part of the cell, and is surrounded by only a
narrow transparent zone without granules. The central portion of this gran-
ular mass is, says Reichert, more translucent than the peripheral, owing to the
presence of a nucleus. The centre of the nucleus, whose outline it is difficult
to see, is occupied by a dark round spot, the nucleolus. Immediately around
the latter (therefore inside the limit of Reichert’s nucleus) the fat granules
(Fettkérperchen) look like little dots, but toward the periphery they are of
increasing length, so that the outermost present the appearance of little rods, —
all pointing toward the centre of the cell.
In the excellent studies of Dr QUATREFAGES (48, p. 177, Pl. III. Fig. 11)
on Hermella is contained an allusion which is probably referable to a central
stellate figure, whose delicate rays, however, remained undistinguished.
KRoun (’52, pp. 314, 315) seems to have been the first to notice an amphi-
aster, although he did not, after all, make special note of any connecting
structure between the two stars. In artificially fertilized eggs of Phallusia
mamumillata, he observed that at the approach of each segmentation the clear
vesicular nucleus disappears, and that in its place there is found in each seg-
menting sphere a very peculiar arrangement of the yolk moleculés. These
granules, namely, dispose themselves in thick-set streaks (dichte Streifen),
which appear to arise from two centres of radiation (Irradiationscentren),
whence they are directed outward toward the lighter periphery. By the time
the nuclei have made their appearance within the new cleavage spheres, the
radial streaks have disappeared.
The paper is without accompanying figures, but the description is so accurate
that it leaves no doubt as to the real nature of the rays.
A few years later, Reichert’s observations were confirmed by MEISSNER (’54, p.
209, Taf. VI. Fig. 1), who found the radial structure both in the parent cells
MUSEUM OF COMPARATIVE ZOOLOGY. 247
(Keimzellen) and daughter cells, from which the male elements of reproduction
are developed in Nematodes. In Ascaris mystax, A. marginata, A. megalo-
cephala, and A. depressa, the same phenomena were observed. After the dis-
appearance of the nucleus of the parent cell, the granules retreat a little from
the cell wall, and begin gradually to assume a very uniform radial arrangement,
like acicular crystals emerging from a somewhat clearer common centre. There
is no nucleus in this centre, but the granules there are fine. (This whole
granular portion Meissner erroneously considered to be the nucleus, Kernmasse.)
The centre of radiation, hitherto single, becomes indistinct, and gradually a
double or multiple arrangement makes its appearance, while the nucleus be-
comes constricted. The centre of radiation moves continuously toward, and
finally attains, the centre of the new nuclei (Kernmassen), which furnish the
basis for the formation of the corresponding cells.
The passage in REMAK (’55, p. 132) cited by Whitman (78%, p. 16) as evi-
dence of the former’s observation of a radial arrangement of the yolk substance
in the segmenting eggs of Rana, does not seem to me as convincing as one
might wish. That Remak himself had no such conception of the nature of the
appearances figured (Taf. IX. Fig. 2, op. cit.) must, I think, be tolerably
evident from the context.* The passage (compare Taf. IX. Fig. 2 of Remak’s
work) in question (§ 10, p. 132) is as follows: “ Legt man die Halften des
Eies in diesem Zustande [i. e. during the first segmentation] aus einander, so
erkennt man an beiden durchaus gleiche Beschaffenheit der Innenflachen :
zunichst eine centrale runde oder ovale Bruchflache von kérnigem Gefiige und
von wechselendem Umfange, so zwar, dass sie den gréssten bis herab zum
kleinsten Theil der Innenflaiche einnehmen kann. Die scharfe Grenze der
Bruchflaiche wird durch den Uebergangsrand der beiden Scheidewande gebildet:
sie macht sich durch die Glatte und Farbung der letzteren leicht kenntlich.
Im Bereiche der unteren Hihalfte sind die Scheidewainde durchaus weiss oder
weissgelblich, also in ihrer Farbe nur wenig von dem angrenzenden Zooplasma
(Dotter) verschieden, dagegen nehmen sie am Aequator allmiilig eine schmutzig-
graue oder schwarzliche Farbung an. Namentlich sieht man haufig dunkele
Streifen in radialer Richtung von dem schwarzen dusseren Rande der Be-
rihrungsflache, der zugleich die Grenze des freien Theils der Eizellenmembran
bildet, bis zum Rande der Bruchflache sich hinziehen, was die Vorstellung von
einem lebhaften centripetalen Zuge erwekt, mit welchem die Scheidewiinde der
_ Abschniirung zustreben.” It would appear from this, I think, that Remak
located this phenomenon in the “Scheidewande” rather than elsewhere, and
* As is well known, Remak distinguished between what he calls ‘‘ Einfurchung”’
and “Durchfurchung.” The former is accomplished by an annular furrow, which
advances only a certain distance toward the centre of the egg, and is accompanied by
the involution of the ‘‘egg-cell membrane.” From the floor of the furrow thus
formed there proceeds, without (direct) participation on the part of the “egg-cell
membrane,” the formation of a new structure, — partition walls (Scheidewinde), —
which completes the separation of the halves of the segmenting egg. This last sup-
plementary act is consequently called Durchfurchung.
248 BULLETIN OF THE
this view seems to be corroborated by the explanation (p. xxviii.) of the
figure, viz.: “ Fig. 2. s, Die Scheidewand ; im oberen Theile des Eies zeigt
sie graue radiale Streifen.” Also in the explanation (p. xxix.) of Fig. 7a
(same plate): “2, einer an beiden Eihalften sichtbaren weissen Bruchfliche, an
. deren Peripherie die Scheidewand ahnliche radiire Streifen wie bei Fig. 2
darbeitet.” If the rays were thus superficial, as Remak implies, they could
hardly be considered as belonging to a real protoplasmic aster.
It is quite another question whether Remak was right as to the location of
the “ Streifen,” — whether they may not, after all, have belonged to the deep por-
tions of the protoplasm.
An examination of the figures Sahith O. Hertwig (’77, Taf. IV., V.) gives of
the radiate appearances in different stages of the eggs of Rana temporaria fur-
nishes nothing which would warrant us in referring the figures of Remak to
like phenomena. It seems to me that the peculiarities which Remak has
figured may perhaps be due to variations in the thickness of the [thin] pig-
ment-lamella which, according to Hertwig (op. cit., p. 49, foot-note), sinks down
into the yolk at cleavage. Unfortunately Hertwig gives only a profile view
(Taf. V. Fig. 6) of this lamella, from which it is not possible to determine
whether its thickness is subject to alternations capable of producing, as sug-
gested, this radiate effect.
MEISSNER (’56, pp. 374, 375), writing of Echinus, says: “Das Keimblaschen
ist in zur Ausstossung reifen Eier bereits verschwunden; die Dotterkornchen
zeigen eine sehr deutliche radiaére Gruppirung um ein helles Centrum, welches
sich als ein rothlicher, zihfliissiger Tropfen isoliren lisst.. ... Der die Stelle
eines Kerns vertretende réothliche zihflissige Tropfen, der oben erwahnt wurde,
theilt sich und der Dotter sondert sich in zwei Massen, deren jede sich um ein
Centrum wieder radiair gruppirt.”
The following year GEGENBAUR (57, p. 7, Fig. 3) described similar appear-
ances during the first and second segmentations of the egg of Sagitta. A little
while after the segmentation has been accomplished, the fine molecules of the
yolk each time appear collected in a greater abundance around the nucleus,
forming radial streaks (Streifen), which gradually disappear toward the pe-
riphery.
Further observations on the sperm-cells of Nematodes were made by Munk,
Walter, and Claparede.
Munk (58, pp. 382-391, Taf. XV. Figs. 11-14, 25, sa figures the structure
in question for both parent and daughter cells. The “strahlige Anordnung”
was observed in Ascaris mystax, A. marginata, and A. megalocephala (p. 382).
In the formation of the four daughter cells, “ The clear central nucleus of the
‘radiate cell vanishes, and there appear nearer the periphery two new clear
places, each of which becomes again the centre of a radial arrangement of the
granules.” Then follows the division of the cell. This process is then repeated
on each of the new cells in like manner. When the four daughter cells have
become free, the “strahlige Anordnung” of the granules soon disappears, and
needle-shaped granules are no longer to be seen.
MUSEUM OF COMPARATIVE ZOOLOGY. 249
WALTER’s (’58, p. 493, Taf. XIX. Fig. 31. C. 6-8) observations relate to the
sperm-cells of Oxyuris ornata, of which he says that, while the cells are
growing, a granular mass is gradually deposited around the nucleus, which by
and by assumes the well-known radial figure peculiar to some Nematodes.
CLAPAREDE (’59, pp. 52, 60-63, Pl. V. Figs. 16, 17, Pl. VII. Figs. 3, 4) con-
firmed the observations of Reichert and Meissner so,far as regards the occur-
rence of a radial arraugement of the granules in the sperm-producing cells of
Ascaris mystax, etc. ‘The nucleus entirely disappears, even beyond the possibility
of being recalled by the use of acetic acid. Then the granules, hitherto irregu-
larly distributed, move toward the periphery and arrange themselves in rays
about a clear non-granular centre. In this stage the cells undergo a prolifera-
tion. The nucleus (i. e. the granular mass, which Claparede does not, however,
confound with the clear nucleus, now disappeared) divides indifferently into
two, three, or four parts. At first there are formed two or three clear spots at
the centre of the granular mass ; gradually these separate from each other, and
around each of them the granules arrange themselves in rays. Thus are
formed several masses with radial structure. The cell suffers constriction
around each of these nuclei, and is finally divided into as many daughter
cells as there are new nuclei. Claparede is probably wrong in considering
these granular masses nuclei, for they must correspond to the asters which be-
long properly to the protoplasm surrounding the nucleus.
In the case of Phallusia mammillata, KowaLEvsky (66%, p. 4, Taf. I. Figs.
2, 3) has given very clear drawings of optical sections of the cleavage spheres
after the first and second segmentations. Concerning the radial phenomena,
he says: “Die Dotterkérnchen der Furchungskugeln liegen strahlenformig
gegen den Kern.”
LEeucKaRrt (’67-76, p. 90) also alludes to the same phenomenon when he says
of the first segmentation in Ascaris: “ Die Dottermoleciile gruppiren sich um
die aus einander riickenden Blischen, wie um ihre Mittelpunkte.”
While Kuprrer (’70, p. 128) corroborates for Ascidia canina the previous ob-
servations of Kowalevsky on the radial arrangement of the yolk granules about
the nuclei of segmentation spheres, he places emphasis on the fact that it is not
peculiar to segmentation spheres, since one finds it as much, if not more, pro-
nounced in ovarian eges after they have become altogether granular; “ es-
pecially in the immediate periphery of the germinative vesicle the arrangement
of the granules is at times so regular that one fancies he sees a crown of rods.
Kowatevsky (’71, Taf. IV. Figs. 26, 28, 29) has represented a delicate radial
structure 7 what he considers the nuclei of the cleavage spheres in the case of
Kuaxes. That Kowalevsky considers this clear radially streaked protoplasm
to be the nucleus, is sufficiently evident from his explanation (p. 68) of Fig.
26. I think it is quite certain, however, that the radiate structure is no part
of the nucleus, but is homologous with the molecular asters of the yolk, as
Butschli (76, p. 398) has already pointed out.
The studies of Schneider and other recent observers who have seen astral
figures will be considered further on.
250 - BULLETIN OF THE
There have been observed numerous radial phenomena, which, at various
times, appear in different parts of eggs and other cells. These observations,
to most of which my attention has been directed by Biitschli (’76, pp. 387,
388), are, I believe, not all based on phenomena homologous with one another,
to say nothing of their being identical with molecular asters. Many of them
relate to the eggs of vertebrates, and the appearances have in such cases often
been referred to the presence of pore-canals. In how far any of them may be.
referred to the same causes which induce the temporary radiate structures now
generally known as asters, can perhaps be satisfactorily determined only by
reuewed studies. Without additional investigation it seems hardly justifiable
to assume, with Biitschli, that all such phenomena are identical. Among
the several cases which he cites, the observations of Eimer (’72%, p. 219,
Taf. XI. Fig. 3) exhibit as strong evidence as any that they are based on the
study of asters ; for the thick transparent membrane about the germinative
vesicle is not very sharply limited from the yolk substance, the radiation about.
the vesicle is not fully restricted to this clear zone, and the early disappearance
of the structure points to the unstable and temporary character of the phenom-
enon in this case. Still, I think it may be doubted if any of the cases
cited below show very close relationship with the molecular asters, since the
latter rapidly appear and disappear in advanced stages of the maturing egg,
and during segmentation. Whereas the real asters seem to point to a funda-
mental rearrangement of already acquired substance, the appearances in most
of the cases cited seem either to sustain important relations to the acquisition
of new material, or to represent other permanent structural differentiations of
the cell. .
REICHERT (56, pp. 103-124, Taf. IT., III.) has described at length a peculiar
structure of the nutritive yolk in mature and fertilized eggs of the pike. At first
sight the radiate structure in this case presents a striking resemblance to molec-
ular stars, and more particularly to those modified spiral asters which have been
traced in Limax during the formation of the polar globules. There seems,
however, to be little ground for considering them in any way homologous.
Reichert states that traces of the radiate structure are to be seen in fresh eggs,
although much more distinctly when hardened in acid or alcohol. In sections
of eggs thus treated, the striation may be seen with the unaided eye. The whole
nutritive yolk is traversed by light and dark radiating streaks. These extend
from: the whole periphery, apparently converging at the centre of the yolk.
This central region, or vertex (Scheitel-Region), is not spherical ; its greatest
extension corresponds with the sagittal plane of the embryo. The rays, rarely
rectilinear, usually take a protracted S-shaped course. The streaking is some-
what finer at the posterior portion of the yolk than elsewhere, and is coarser in |
the middle part of each ray than at either end. The rays are due to fine canals
which traverse the yolk from the periphery, where they begin with narrow -
openings, to near the centre. Instead, however, of terminating at the centre,
they curve backward toward the surface. Each canal thus becomes continuous
MUSEUM OF COMPARATIVE ZOOLOGY. 251
with another radial tube of its own hemisphere, and the two describe a par-
abolic curve convex toward the centre of the yolk. The canals contain a
liquid albuminous substance. In diameter they vary from 0.01’ to 0.0025’”
(22.6 p to 5.6 »). They may subserve, according to Reichert, the purpose of an
exchange of substance between the yolk and surrounding media, through a
process of diffusion.
These canals continue to be traceable during the growth of the embryo, until
the yolk is reduced to a very small mass.
PFLiGER (63, p. 79, Taf. V. Fig. 7) describes the “inner yolk” of the nearly
mature egg of the cat as being often quite sharply limited from the “ outer yolk,”
and still as presenting at the periphery a radial condition. One sees, he says,
that at different, though not numerous places, sharply limited processes (which,
I may parenthetically add, are very broad, and in no way recall the familiar
aster) reach out from the inner yolk to the zona pellucida. “ Man konnte dies,”
he continues, “auch so auffassen, dass man sagte, es bestande im Eie um das
Keimbliaschen eine Hohle, welche durch radiiir verlaufende sich allmahlich
verjiingende Canile mit der zona pellucida zu communiciren scheint.”
The observations of ORLLACHER (’72, pp. 6-14, Figs. 3-10) on trout eggs led
him to the conclusion that, while the egg is still in the ovary, the germinative
vesicle approaches its surface, and that the thick radially striate membrane of
the vesicle subsequently becomes evaginated through an opening at its most
superficial point. The contents of the vesicle thus become eliminated from the
ego, and the thick membrane is spread over a considerable portion of its sur-
face asa thin veil (Schleierchen), which still continues to exhibit the radial
(now palisade-like) structure. In the opinion of the observer the alternat-
ing dark and light striations are due to pore canals; the lumen appears dark
(in a surface view as dark points), and the walls give rise to the light bands.
Biitschli inclines to the opinion that in this case the so-called membrane of
the vesicle is only a portion of the formative yolk which has become radially
striate. But, to judge from Oellacher’s Figure 6, the effect of this. striating
influence does not extend into the yolk deeper than the rather sharply limited
substance called membrane, and its persistence throughout all the vicissitudes
of an evagination and ultimate elimination from the yolk bespeak for it a me-
chanical condition which is hardly paralleled in the molecular asters.
In the eggs of certain snakes Ermer describes ('72%, pp. 219, 220, 427, 428, Taf.
XI. Fig. 3) the germinative vesicle as surrounded by an inordinately thick,
very peculiar envelope (Hiille), “die aus sehr feinen Kérnchen zusammen-
gebacken scheint und sich durch eine schéne radiare Streifung auszeichnet.”
In some places the rays are traceable into the surrounding yolk. In smaller
eggs one finds only a. thin membrane ; in those that are larger this phenomenon
has disappeared, and there remains simply the thin membrane. Eimer ex-
plains this appearance as due to pore canals. “ Die radiire Streifung ist wohl
als der Ausdruck von Poren, von feinen Rohrchen zu erkliaren, welche die Hille
durchsetzen.”
In addition to this circumvesicular striation Eimer (72%, p. 228, Taf. XI.
5
202 BULLETIN OF THE
Figs. 8, 12, 14) describes radial structures in the cortical portion of the yolk,
which are due, in his opinion, to the inward prolongation of the trumpet-shaped
cells of the granulosa.
It is ev vaya to this latter structure that ScHuttz (’75, pp. 577, 578, Taf.
XXXIV. Figs. 8, 9) alludes when— comparing his own chacunalanet on the
structure of the egg of Torpedo with those of Eimer —he says : “ Notwithstand-
ing a superficial agreement, a genetically determinable analogy is wanting, inas-
much as Eimer derives the protoplasmic streaks in the yolk of the reptilian egg
from the penetration of the egg envelopes by the protoplasm of the cells of the
granulosa, — a thing which must be absolutely rejected for the egg of Torpedo.”
The protoplasmic streaks in the egg of the Torpedo occur, according to Schultz,
in the peripheral zone of the yolk as a series of wedge-shaped groups of fibres
(Strange) which consist of faintly granular protoplasm. The bases of the wedge-
shaped groups are directed toward the periphery, and the radial fibres are con-
nected with an irregular network which occupies the balance of the peripheral
yolk.
In addition to these observations to which Biitschli has called attention, it
may be observed that Leypie (’57, pp. 14, 346) has reported a structure similar
to that of the so-called membrane of the germinative vesicle in the nucleus of
certain large cells found in the “fat body” of Phryganea and other Arthropods,
and does not hesitate to predict that this pore-canal structure may in the future
be demonstrated in other cases.
In Fig. 194 (p. 362, op. cit.) Leydig has represented the secreting cells in the
tip of the liver tube of Gammarus as conspicuously radiate in structure about
the nucleus as a centre.
SEMPER (57, p. 361, Taf. XVI. Fig. 3) figures large connective tissue cells
from the stomach of Lymneus in which the nuclei are surrounded by a
narrow zone of finely granular substance, which is depicted as stretching out
in irregular rays.
KOLLIKER (’57, p. 92), moreover, has observed a radiate stmeteieaete in the wall
of the germinative vesicle in young eggs of Gadus lota, which he thinks may be
due to pores. He adds: “ Da nun auch der Dotter, so lange er noch feinkornig
ist, manchmal wie dusserst fein radidér streifig erscheint, so wird einem der
Gedanke nahe gelegt, ob nicht vielleicht der ganze Stoffwechsel der Eizellen in
bestimmten radiaren Bahnen vor sich gehe u. s. w.” Compare also Kolliker,
"63, p. 17.
In the “ Parenchymzellen” of Lampyris, Max Scuuttzx (65, Taf. V. Figs.
4, 5) has also figured radiate appearances, similar to those represented by
Semper, in the immediate vicinity of the nucleus.
OELLACHER (’72°, pp. 375, 376) has also observed, in the nutritive yolk of the
trout’s egg hardened in weak chromic acid, canals similar to those described
by Reichert which open on the surface of the yolk beneath the vitelline mem-
brane. The contents of the canals, of unknown composition, appear trans-
parent and colorless. On the broken surface of eggs hardened in more con-
centrated acid (4-1%) a radial, striate texture is discernible. Both this and
MUSEUM OF GOMPARATIVE ZOOLOGY. 253
the canals aré doubtless dué to peculiar ‘structural conditions of the fresh yolk,
though it is doubtful if they are ideittical. :
BaLBIANI (’73, p. 77, Figs. 40, 79, 80) has seen a stellate arrangement of the
protoplasm about the nucléts as a céntre-in any blastoderm be of Epeira in a
fresh condition. ° adiad, Res er '
3% TARE TTR PRE Spas oI AF
Of interest in this connéction are also ‘the stellate ‘differentiations i in the pro-
toplasm-6f certain Rhizopods. el ny Sid
“GRENACHER -('69, p. 292, Taf, XXIVSFig. 1. d) describes for Acanthocystis
viridis an irregular’central space filléd with an apparently watery fluid, and
located in the centre‘ ofthis a minute, pale corpuscle, from which radiate on all
sides numerous likewise" pale, fine "filaments, which fully agree with the axial
filaments ‘of * es A ditect continuation into the pseudopodia was
not: observed.» Lk ash !
GREEFF (a 4 6) confirms Grenacher’s observation for A. viridis and other
species, as also for Actinophrys Eichhornii, and finds the rays to Be continu
ations « of the axial filaments of the pseudopodia.: = 8° 84 oe er
J Séiurzd (74%, pp. 380-382, Taf. XXVI. Fig. 1) has‘also Shdirdeas a Merkle
structure in ‘the’ cdse of Raphidiophrys pallida, and established ‘beyond doubt that
it is not with a siliceous skeleton that one has to.do. Schulze’s experiments,
however, also show conclusively, if proof were at all needed, that’ thestructure
in question ¢an have nothing in common with molecular asters, which are not
destroyed, like the radial structures in Rhizopods, by acetic acid.
b. QUIESCENT NUCLEI.
Many exceptions to the idea that the nucleus is a homogeneous compact
body have been recorded by the earlier embryologists and histologists, but it is
only within a comparatively short time that general assent has been given
to the belief that it is often an extremely complicated structure.
Owing to their size, the nuclei of egg-cells have been much studied. In cer-
tain animals, especially the lower vertebrates, they have attracted attention
from the great number, and often the peculiar arrangement, of their nucleoli ;
as, for example, in the case of Alytes and several fishes studied by Vogt (42,
pp. 1, 4, 15, Taf. 1. Figs. 1, 2), in Cyprinus auratus according to Meckel von
Hemsbach (52, p. 421, Taf. XV. Fig. 1), in turtles as described by L. Agassiz
(57, pp. 475-479, Pl. VIII., [X.), and in Rana as more recently investigated
by O. Hertwig (77, p. 36, Taf. IV. Fig. 1).
The following authors, especially, have made interesting contributions to our
knowledge of the structure of the nuclei of eggs not in process of division.
According to Ermer (’724, pp. 216-220), the germinative vesicle in reptilian
eggs is of an exceedingly complex nature. The nucleoli are subject to the law
of concentric arrangement which the author has elsewhere pointed out for the
nuclei of other cells. This arrangement reaches a culmination in such stages
as are represented by him in Taf. XII. Fig. 18. The germinative dots are also
————oro™——“—~—
254 BULLETIN OF THE
of a vesicular nature. In Tropidonotus natrix the centre of each such vesicular
space is occupied by a “ Schron’s grain,” and in this are embraced a number of
fine granules (Keimptnktchen).
KLEINENBERG (’72, p. 41, Taf. II. Fig. 12) was probably the first to call at-
tention to a differentiation ae the contents of the germinative vesicle into “a
viscid, plasmoid, filamentous mass and a more fluid substance.”
In his paper on Hydra, it is shown how, by a process of vacuolation, the
contents of the germinative vesicle are separated into a continuous thin layer,
lining the nuclear membrane, and a thicker mass concentrated about the ger-
minative dot. The intervening space is filled by a fluid clear as water. The
latter is traversed, however, by numerous delicate filaments, which connect the
peripheral and central accumulations of granular protoplasm.
Since the appearance of this paper, the reticular nature of the germinative
vesicle has often been observed ; for example, by Flemming (’75, p. 100, Taf.
I. Figs. 14-20) in fresh eggs of Unio; O. Hertwig (75, pp. 351, 352, Taf. X.
Fig. 1, Taf. XI. Fig. 9) in fresh eggs of Toxopneustes and in the eggs of
the mouse ; Ed. van Beneden (’75, p. 690, "764, p. 64, Fig. 9, "76%, p. 170, PI.
XIII. Fig. 9) in the rabbit and Asteracanthion ; * Biitschli (’76, p. 218, Taf. I.
Figs. 6-8) in Nephelis ; R. Hertwig (76%, p. 77, Taf. III. Figs. 8, 9) in the sea-
urchin and the frog ; Giard (’774, p. 720,’774, p. 434) in Echinus miliaris ; Fol
(77°, p. 440) in Asterias, Sagitta, etc. ; Hoffmann ('77%, p. 33) and Whitman
(784, pp. 13, 14, Pl. XIII. Fig. 61) in Clepsine; and Balfour (’78?, pp. 412, 418,
37) in Scylliam.
Beside an intranuclear network of finely granular pale substance in the
germinative vesicle of Unio and Anodonta, FLEMMING (’75, pp. 95-105) dis-
covered that eggs which have attained a certain stage of development embrace
in their nuclei not a single, but two apposed nucleoli. These differ in their
reactions and in size. The one, which is called the principal nucleolus (Haupt-
theil), resists more the action of acetic acid, and is stained more deeply than
any other part of the vesicle. The other, which is called the accessory part
(Nebennucleolus), exhibits the same reaction as do large numbers of smaller
nucleolar structures which are distributed through the network and which vary
greatly in size. They are all more readily affected (swollen) ‘by acetic acid,
and are less intensely stained than the Haupttheil. The nuclear contents are
still less stained, and the intranuclear cords become in stained objects invisible.
The accessory nucleolus, at first absent, is, during early stages in the growth of
the egg, smaller than the principal nucleolus, but ultimately exceeds the latter
in size. Flemming is inclined to regard the accessory part as a product of the
main nucleolus (constantes Quellungsproduct) but not as resulting from divis-
ion. For this reason the multinucleolar condition of a nucleus may be regarded
in a different light from that in which Auerbach (’74) has considered it.
TRINCHESE (’76) was the first, I believe, to call attention to the reticulum
in the germinative vesicle of the (immature) human ovum. He characterizes
* This network is the nucleoplasm of Van Beneden.
MUSEUM OF COMPARATIVE ZOOLOGY. 255
it as a network of very delicate protoplasmic filaments composed of a homo-
geneous matrix and of granulations arranged in line. Within this network,
which stretches through the whole cavity of the vesicle, the germinative dot is
suspended, so that the filaments which, by their ramifications and anastomoses,
form the network proceed from the dot. A similar reticulum is found in the
ease of the cat, the rabbit, and mollusks. In the latter instance, there are, be-
side the germinative dot, other smaller spherical corpuscles, one to seven in
number, which are’ intensely stained in hematoxylin, or carmine. A short
distance from the germinative dot is sometimes seen a pale transparent vesicle,
which is not stained.
In a subsequent note Trinchese (’77) finds, in addition to the principal
germinative dot and several accessory ones,* an irregular body, to which he
gives the name “grumo” (clot). This presents prolongations which are con-
tinuous with the network filling the cavity of the germinative vesicle. The
germinative dot and the grumo are both stained in hematoxylin; if sub-
sequently submitted to ammoniacal carmine, the dot remains violet, but the
grumo is stained red. |
In his recent paper on the structure and development of the vertebrate ovary,
Batrour (’78°) has given considerable attention to the structure of the nuclei,
especially those of developing ova, and the successive changes which they un-
dergo, — changes that are not brought into connection with cell-division. The
ovaries studied were those of selachians (Scyllium, Raja) and mammals (princi-
pally rabbits). During the conversion of primitive into permanent ova (Scyl-
lium) the nuclei undergo certain alterations which are the same whether the
primitive ova retain their individuality and all become permanent ova, or in
groups suffer a confluence into polynuclear masses (syncytia), out of which result
a diminished number of permanent ova.t The nuclei increase in size, and, in
place of being granular, become delicate vesicles filled with a clear fluid, con-
taining, close to one side, a granular mass, which stains very deeply with color-
ing reagents. The granular mass becomes more or less stellate, and finally
assumes the form of a reticulum, with one or more highly refracting nucleoli
at its nodal points (p. 416). Balfour thinks that the deeply staining granular
mass constitutes a part, but not, as is maintained by Semper, the whole of the
nucleus (p. 393). In addition to the ordinary mode of increase for nucleoli (viz.
by division into two), there sometimes appears to be a production of numerous
smaller nucleoli within a larger nucleolus, comparable with endogenous cell-
formation. These nucleoli doubtless become free. Certain structures, variable
in size, which are found in the yolk, are thought to be nucleoli thus set free
(pp. 412, 413). The reticulum, which is conspicuous in the germinal vesicle of
freshly formed ova, becomes granular and less distinct in older ones. The
* A misprint in the Jahresbericht of Hofmann and Schwalbe (Bd. VI., Anat., p. 15)
makes Trinchese appear responsible for the existence of several ‘“‘ Keimbldschen.”
f A portion of the nuclei in the latter case atrophy and become “ pabulum for the
-Temainder”’; the metamorphosis of these is, of course, not embraced in what follows.
|
256 BULLETIN OF THE
nucleoli (1-3) increase gradually in number as the vesicle grows older, and
often lie in close proximity to the membrane.
Similar observations are made (pp. 425, 432) on the nuclei of mammalian ova.
“ The nucleus of the cells [germinal epithelium] loses its more or less distinct
network, and becomes very granular, with a few specially large granules (nu-
cleoli). The protoplasm around it becomes clear and abundant, — primitive
ovum stage.” “ A segregation takes place in the contents of the nucleus within
the membrane, and the granular contents pass to one side, where they form an
irregular mass, while the remaining space within the membrane is perfectly
clear. The granular mass gradually develops itself into a beautiful reticulum,
with two or three highly refracting nucleoli, one of which eventually becomes
the largest and forms the germinal spot par excellence.” Klein’s statement that
the “nucleoli” are accumulations of fibres is too sweeping, according to Balfour,
since nucleoli often exist in the absence of a network, and the latter is certainly
wanting in primitive ova. The differences of opinion between Balfour and
Klein are not very radical, however, for the former considers that both network
and nucleoli are composed of the same material, — nuclear substance.
There are probably no tissues in which the structure of the nucleus has been
more attentively studied than in the ganglionic cells of nerve centres. It is
the magnitude often attained by them, as well as the lively controversy concern-
ing the relation of the nerve fibres to them and their nuclei, which has tended —
to make the latter the objects of oft-repeated observations.
In 1846 the studies of Har uess (46, p. 287) on the ganglionic cells of the
lobi optici in the torpedo pointed to the union of the nucleolus with one or
two nerve fibres. After treatment with iodine the fibre (Nervenprimitivfaser)
may be traced, says Harless, as a light yellow streak, through the more deeply
colored ganglionic body, up to the nucleus of the inner cell [i. e. up to the
nucleolus].
Similar conclusions were reached by Axmann (47) and Lieberkiihn (’49),
whose results are cited by STILLING ('56~59, pp. 807, 814, 821).* The last
author, though unable to confirm these observations, maintains ('56—59, pp. 783-
787, 793-796, Taf. XXV.) that the parenchyma of cell, nucleus, and even nucle-
olus is traversed, without recognizable order, by numerous extremely fine tubes
(Elementarréhrchen), which together form a dense network. Open as these
studies of Stilling doubtless are to the severe criticisms which have been urged
against them, they nevertheless may not be exclusively the result of a failure to
distinguish between artificial and natural appearances. Recent studies make
very probable the existence of a greater complication of nuclear structure than
has hitherto been generally accepted, though not lending any direct support to
Stilling’s views of the tubular nature of the filaments he has depicted.
WaGENER (’57) defends Lieberkiihn from the criticisms of Stilling (’56), and.
adds evidence drawn from the study of nerve-cells in Hirudo, Limax, etc., to
show the existence of the nucleolar fibre.
* See also Stilling, ’56.
MUSEUM OF COMPARATIVE ZOOLOGY. 257
FROMMANN (’65 and '67) was the first, according to Flemming (78%, pp. 350,
351), to demonstrate on fresh objects, in addition to such as had been hardened,
the existence of branching filaments within the nucleus. Frommann does not,
however, seem to have directly stated that these filaments by anastomosing
completed a genuine network. I have not been able to consult the original
papers by Frommann.
CoURVOISIER (66, pp. 24, 25) finds in nerve cells of the sympathetic system
that “there emerge from the nucleolus, from the innermost centre of the cell,
fibres which are in part coarse and in part almost invisibly fine. These are
most easily recognized in clear nuclei, which they traverse in a radial direction,
and thus adorn with a star-like figure.” They are the “ Wurzelfaden” of
Courvoisier.
It should be added in this connection, that subsequently Courvoisier (68, p.
134) “could not establish with certainty stellar figures in the nucleus— pro-
cesses of the nucleolus” — in the case of the frog. Compare also pp. 142, 143
of the last-mentioned paper.
SCHWALBE (’68, p. 60) has often observed a radial arrangement of the sub-
stance of the nucleus [ganglionic cells] with the nucleolus as centre. The
granules of the latter, however, do not afford confirmation of Frommann’s view,
which would make them to be the optical sections of nucleolar fibres. Vacuoles,
although occurring in nerve cells of Arion (loc. cit., Fig. 15), are not to be found
in those of the vertebrates studied by Schwalbe (p. 63).
ARNDT (’68, pp. 473-492) recognizes no less than four kinds of “ nucleolar
filaments ” in the cells of the cerebrum, but all are, in his opinion, to be other-
wise explained than as structural filaments which traverse the substance of the
nucleus. Either they are the optical expression of fissures in the nuclear sub-
stance, or really lie outside the nucleus, or are due to phenomena of refraction
(p. 476).
After his discovery of a hollow sphere of granules surrounding at some dis-
tance the nucleolus in cells from the skin of the mole’s muzzle,* Ermmr (’72)
extended his observations on the structure of the nucleus, and came to the con-
clusion that this “ Kornchenkreis ” was a very general feature of nuclei in the
full vigor of life. |
The clear area which Eimer described in the first-mentioned paper as im-
mediately surrounding the nucleolus, he finds almost always present. That
portion of the nucleus, however, which lies outside this “ clear area,” and from
which it is separated by the “ circle of granules,” is not always dark, as reported
in his first article, but may present the same appearance as the “ clear area.”
In his paper on the eggs of reptiles Eimer (’724, p. 236) finds further con-
firmation of this peculiarity of the nucleus in the follicular epithelium. He
also gives figures of the division of the nucleolus (Taf. XII. Fig. 26. a) which
strikingly recall certain phases of the process of division in the nucleus as at
present understood.
In studies on nerve cells of the sympathetic system, and on the skin of Sala-
* Kimer, "71, p. 189, Taf. XVII. Fig. 8.
VOL. VI.— No. 12. : 17
258 BULLETIN OF THE
mandra, LANGERHANS (’71, p. 16, Fig. 6,'73¢, p. 750, Taf. XXXL. Fig. 11) con-
firms Eimer’s observation. It may be added that Eprertu (’63, Taf. XIV.
Fig. 2) long ago figured nuclei from the ephithelial lining of the triton’s lung
presenting similar features.
S. MAYER (72, p. 812) says, “ The substance of the nucleus [sympathetic
nerve cell] is not homogeneous ; there may be observed in the same fine fila-
ments (Faden) which arise from the nucleolus.” Although unable to find a
communication of the cell processes with the nucleus or nucleolus, he reports
a little further on (p. 817) his conviction that, very often, in addition to the
processes of relatively large calibre which arise from the cell-substance itself,
still a second system of very fine filaments emerges from the cells which take
their origin in the nucleus and nucleolus.
As part of a scheme of extensive, if not universal, applicability to the
structure of protoplasmic bodies, HEITZMANN (’73 and '73¢) maintains for the
nucleus a reticulation, which is continuous with a similar network of the sur-
rounding cell-protoplasm. The reticulated structure, however, is an indication
of a certain advance in the age of the protoplasmic body. “The originally
quite homogeneous mass of protoplasm becomes differentiated at its periphery —
with accompanying increase in circumference — into a network, while the
centre — the nucleus — remains homogeneous. Then follows a differentiation
in the central mass (nucleus) into a Fachwerk, and later into a network, so that
here also compact, smaller centres remain as nucleoli.”
Finally, the differentiation has taken place in the whole protoplasmic body.
Thus the disappearance of the nucleus is followed by that of the nucleoli; the
whole body is now only a network with coarser or finer nodal points, and this
condition immediately precedes in tissues the formation of a “ Grundsubstanz”
(73, pp. 155-158, and ’73+4, pp. 46, 47).
These general conclusions are supported by observations of vacuolation in
Ameba (73, p. 101, 734, p. 42) ; by studies on blood corpuscles of Astacus *
(73, p. 105); on white blood corpuscles of man (’73, p. 107); on cartilage cells
(73, p. 142, and "734, p. 48) ; on ganglionic corpuscles of the brain and sympa-
thetic centres (73, p. 153); and on some other structures.
- The nucleolus, the nucleus, the granules, and their filaments are the strictly
living, contractile material, and this contains in its reticulations, and encases as
a shell, a non-contractile fluid material, which, however, cannot be pure water.f
* In this case the corpuscles suffer a vacuolation resulting in a network which
gives the protoplasmic reaction with chloride of gold, while the vacuoles remain
colorless.
+ The existence of an extra-nuclear network in the peripheral cells of the salivary
glands of Blatta has been established by the researches of Kupffer ("74, pp. 78-81),
who is not inclined to ascribe a passive importance, or even subordinate function, to
the more pellucid, non-fluid ‘‘Grundsubstanz” through which the network runs.
Compare also Kupffer’s (75) studies on the liver cells of the frog, ete.
An extranuclear reticulum of greater or less extent has been seen by many other
observers in various tissues, but especially in nerve cells from the time of Stilling to
Frommann, Trinchese, Ciaccio, and others.
MUSEUM OF COMPARATIVE ZOOLOGY. 259
Probably no single work within the past few years has furnished a greater
impetus to the investigation of the structure of nuclei than the extensive and
systematic observations published by AvERBACH (’74) in 1874. To avoid the
possible influence of surrounding protoplasm on nuclear reactions, observations
were conducted on nuclei mechanically separated from the cells, as well as on
those left in their natural positions. Liver and other cells from the carp ex-
hibit, besides 1-4 centrally located nucleoli, numerous exceedingly small
and faint granulations (Zwischen-Kornchen) evenly distributed through the
“ Grundsubstanz,” save that a clear area is left about each of the nucleoli and
sometimes a corresponding area just within the nuclear membrane. In Auer-
bach’s opinion, this appearance is due to the repulsive influence of the nucleoli
and the nuclear membrane upon the “ Zwischen-Kornchen,” which are mova-
bly suspended in the soft matrix (Grundsubstanz). Eimer, however, has in
Auerbach’s opinion assumed too much in maintaining that this feature is
general for fully active nuclei, and has reproduced appearances which only
arise with the use of hardening reagents.
There is space here for only a brief statement of the action of reagents
which Auerbach has described at considerable length. Water employed to
gradually dilute the menstruum in which the nuclei are examined first causes
a shrinking in the nucleus, accompanied by the expression of a hyaline fluid
(Wasserschrumpfung). Accompanying this there may be an absorption of
water from the more fluid portions of the nucleus by its denser constituents
(innere Quellung), whereby an apparently homogeneous condition results.
There is not, however, an actual melting together of the constituents. A
more attenuated condition of the menstruum leads to a restorative swelling
(Wiederaufquellung), which may, especially with pure distilled water, cause the
nucleus to swell beyond its original proportions (Ueberaufquellung), but never
destroys it.
Auerbach finds that solutions of common salt, bichromate of potash, acetic
acid, and probably other substances, vary much in their effects upon nuclei, ac-
cording to the degree of concentration employed. The hardening and especially
the shrivelling effect is by no means always in direct proportion to the concen-
tration of the reagent. A shrinking of the nucleus is caused by very dilute
conditions of the reagent (extending from about 1% to 0.01%), and while even
more dilute solutions (up to 0.001%) cause an “innere Quellung,” it appears
that there is often another and quite distinct series of concentrations (extending
in common salt, e. g., from 1.5% to 14%) which produce essentially the same
result. Solutions of sugar, whether concentrated or dilute, cause nuclei to
swell. The shrinking influence of weak solutions of acetic acid and the swell-
ing effect produced by solutions of sugar may therefore be made to counter-
balance each other to a certain extent by a proper mixture of the two reagents,
whereby a comparatively indifferent fluid may be produced. The action of
neutral solutions of carmine is, aside from the staining, essentially like that of
acetic acid.
These results, obtained by the treatment of nuclei mechanically freed from
260 BULLETIN OF THE
the surrounding cell protoplasm, are corroborated by the deportment of nuclei
which remain itracellular, the only modifications being such as are naturally
referable to the intervention of a protopl asmic layer surrounding the nucleus.
Inasmuch as this protoplasm appropriates to itself a definite portion of the
available substance of the solution, it is clear that it must exert a greater modi-
fying influence when the solution is highly.attenuated, than when it is more
concentrated, —a conclusion which accords, with the observed phenomena.
Of more importance for us.than the confirmatory evidence of these views de-
rived/from the study of the nuclei of muscle, cells, red. blood corpuscles, etc., are
conelusions reached in the second division, of Auerbach’s papat concerning the
origin, increase, and.vital properties of nucleoli. .,.....«. sictih Vd
» Contrary to the opinion then commonly accepted, that the signage eupal
contains one,or, two, at most. three or four nucleoli, Auerbach insists that the
presence of more than four nucleoli: is very often a typical.condition, and. that
their number may amount to a hundred or more in extreme cases. _ This con-
dition is as arule the result of successive: self-divisions of previously. existing
nucleoli, and the solitary nucleolus often has the same origin; the latter, how-
ever, may have an independent origin (Neubildung).
On the strength of his own observations in the case of. frogs’ eggs. and the
blastoderm. of Musca vomitoria, supported by evidence drawn from previous
observers, Auerbach concludes that in a certain first stage of, embryonic, develop-
ment in the eggs of vertebrates, articulates, and worms.the nuclei of the young
cells. are dastiante of nucleoli. . It may, moreover,.;/be, supposed, he says, that
this enucleolar condition is for animals a constont Bera ant of a general law of
development (p. 89). atte
In further elaboration of Reichert’s law. of successive se uaeestaetan the author
concludes that in the beginning of organic life there is present only protoplasm,
with or without yolk elements. In a second stage a differentiation of the pro-
toplasm results in the formation of a homogeneous nucleus in the centre, A
third stage is characterized by the appearance of a nucleolus in the centre, and
a nuclear wall at the periphery of this nucleus. The last-mentioned structures
are believed to arise directly from the protoplasmic bady-ef. the cell rather than
from ‘a differentiation of the nucleus}-— the aucleolus.to arise by the detachment
of protoplasmic molecules from the protoplasm. immediately surrounding the
nucleus, which then migrate toward the centre, of the,. soft nuclear mass (p. 84).
Finally, a fourth stage is characterized by the appearance of intermediary
spherules (Zwischenkiigelchen) between nucleolus and nuclear wall. In case
division ensues, the nuclear structures mentioned may be directly transmitted to
the daughter nuclei, or it may be that the daughter nuclei are at first destitute
of nucleoli.
Auerbach brings to the discussion of the relation between uninucleolar and
multinucleolar nuclei an extensive series of observations upon various tissues
of vertebrates, from which he feels justified in maintaining the existence of a
parallelism between the Amniota and the Anamnia in so far as regards the
predominance of multinucleolar nuclei. in. the higher representatives,,of, each
MUSEUM OF COMPARATIVE ZOOLOGY. 261
phylum, and of paucinucleolar nuclei in the lower members of each group
(viz, fishes ,and,, reptiles)., What is.thus established as a probable order, of
succession ,in.a phylogenetic sense, is;sshown to be unquestionably true .in the
ontogeny of certain species, especially in the case of numerous tissues of Musca,
where the growth of the larva is accompanied with a corresponding increase of
nucleoli from one up to thirty or more. This increase, of nucleoli is probably
effected by successive divisions of. the single nucleolus, and is accompanied by
a gradual approximation of the nucleoli to the wall of the nucleus, perhaps as
a result of an.attractive influence exercised by the nuclear membrane, There
are, he thinks, certain important reasons for considering the nucleoli to be of
substantially the same nature as the. cell.protoplasm, of young cells, viz:
1. Certain resemblances:in their optical.conditions; a
-2 The.similarity of their micro-chemical-reactions;,) ose sou
sid The. tendency..of- Jarge nucleoli to-vaeuolation; ~ ..« «+
4...The changes.of form (amceboid) inthe neni and eae
_ 5, The growth and.self-division of the nucleoli;,,
_ Aga natural deduction the nucleoli are considered as SE Sere organisms, —
the equivalents of cytodes, or, if vacuolated, of, nucleated. cells,* —and the nu-
cleus becomes from this point of view a breeding chamber (hohler Brutraum)
in swhich. the;(endogenous) daughter,,cells (nucleoli) arise.. Finally, attention
is-drawn te, the possibility ofjidentifying the liberation of such endogenous
daughter.cells.with the histolytie, processes described by Weismann.
. In; extension ,of .Heitzmann’s. studies on the: blood corpuscles of Astacus,
FROMMANN (75, pps: 289-294) has produced very interesting drawings of the
nuclear and cellular reticulum met with in cells, which are probably also blood
corpuscles of Astacus, though I believe no definite statement is made as to
the source of the cells figured. Frommann was unable to verify Heitzmann’s
observation as-to.the method in which the vacuolated grains give rise to a
closed system of network, especially since it could not with safety be denied
that.the apparently hyaline protoplasm took part in the formation of its
filaments...
_ “The a of yee ganglia i in the crayfish vile moaulla confirmatory. of
statements made. by 1 him in a previous paper. The membrane of the nucleus
is not. of uniform . thickness ; ; there are, namely, within the nucleus granules
and nucleoli which are closely apposed to, or fused with the membrane. The
nucleoli are from three to ten in number, oval, round, or 3- to 4-angled, and
may contain a more highly refringent grain in the centre. The angles: are
drawn out into coarse fibres, and there are, beside, finer threads connecting the
nucleoli to surrounding granules, which in turn are joined to each other by
short filameuts. The nucleoli may. be replaced by compact -grains. and: fine
granules. The filaments of the cell protoplasm unite with the nuclear: mem-
brane, with granules in it, or with nuclear granules lying inside the membrane, —
in short, a direct connection between intra- and extra-nuclear network.
* This recalls the view which Vogt (’42) entertained-concerning: the nature of the
*Keimflecke” of the germinative vesicle in fishes and amphibians. —
262 BULLETIN OF THE
Ep. VAN BENEDEN (764, p. 65, Figs. 20, 21, "76% pp. 170, 171, Pl. XIII. Figs.
20, 21, '76°-4, pp. 1188, 1193, Pl. I. Fig. 15, Pl. II. Figs. 19, 20) has described
a nucleoplasmic network found both in the nucleus of the immense axial cell,
and in that of the ectodermic cells of Dicyemide. It may traverse the nucleus
in all parts, or may be more or less restricted. It is not found in young nuclei.
The nuclear substance is stained rose-color in osmic acid followed by picro-
carmine, and the nucleolus and nuclear membrane bright red, but the net-
work is not stained.
TRINCHESE ('764, p. 175, Tav. II. Figs. 9, 29, and 32-38) confirms the exist-
ence of a previously announced ('76 and '76%) network in the substance of
the cell and nucleus. In the present paper he shows its existence in epi-
thelial cells, connective-tissue cells, and the cells of the albumen gland of
Caliphylla mediterranea, and in the cornea of the frog. The points in which
the filaments of the network meet present nodes or enlargements ; one of these
nodes within the nucleus, somewhat larger than the others, is the nucleolus.
Studies on ganglionic cells of the retina of sheep, calves, etc. lead SCHWALBE
(76) to the conclusion that the nucleus is differently organized at different
stages of development. The smallest, and therefore youngest, nuclei (calf) are
without the trace of nucleoli, and appear to consist of a uniformly distributed
granular mass. This appearance is probably due to a netlike structure, but as
yet there is no differentiation into contents and nuclear membrane. In larger
nuclei 2 - 4 nucleoli are found within a clear mass, which is surrounded by aso-
called nuclear membrane. Some of the nucleoli are intimately blended with
the nuclear membrane, — appear as elevations upon its internal face. These
become less conspicuous in larger nuclei, which usually contain but a single
nucleolus, which is not attached to the membrane. In the sheep, ox, etc., this
internal nucleolus exhibits thread-like prolongations which differ in extent and
number in different cells. Schwalbe’s interpretation of the observations is as
follows.
The substance of which subsequently the nuclear membrane and the nucle-
oli consist — “ nucleolar substance ” — is at first uniformly distributed through
the whole nucleus. This it fills, more or less completely according to the
abundance of numerous small vacuoles distributed through it and containing
another mass, “ nuclear sap.” Inthe growth of the nucleus there is an increase
in the nuclear sap, without an essential increase of the nucleolar substance.
The result is that the latter is sundered into various portions, one of which
occupies the surface of the nucleus (nuclear membrane with its nucleolar ele-
vations), while the other portions constitute the one or more contained nucleoli.
Further increase in size induces a stretching of the membrane, which in turn
causes its elevations to disappear. The whole process is a vacuolation. The
nuclear sap, though probably a fluid, is by no means water, but contains al-
buminoids, salts in solution, and is at least of complicated chemical composi-
tion. The nuclear membrane and nucleoli, whether central or mural, consist
of the same lustrous homogeneous substance.
Schwalbe agrees with Auerbach that in the growth of the nucleus an enu-
MUSEUM OF COMPARATIVE ZOOLOGY. 263
cleolar precedes a nucleolar condition, but does not believe, with the latter
observer and Klebs (’74), that the nucleoli migrate from the cell protoplasm
into the nucleus. Schwalbe agrees with Heitzmann so far as regards the ex-
istence of an intra-nuclear network, but not in its connection with an extra-
nuclear (or cell) network.
The principal conclusions reached by R. HERtTWwIe (764) in his study of nu-
clei have been summarized by the author himself as follows : —
“1. The most important and characteristic part of the nucleus is the nuclear
substance (‘ Kernsubstanz’), an albuminoid which, though possessing
much in common with protoplasm, differs from the latter in numer-
ous peculiarities.
“9. The nuclear substance is imbued, to a different extent in different nuclei,
with a fluid, the nuclear sap (‘ Kernsaft’).
‘3. Primitive nuclei are simply naked masses of this ‘nuclear substance.’
“4, From this primitive form of nucleus the remaining forms are derived by
the following differentiations : —
a. The development of a nuclear membrane (nuclei of Inftsoria).
b. The separation of the nuclear substance from the nuclear sap,
whereby the latter
a. is irregularly distributed in the nucleus and forms numerous vacu-
oles, or
B. is disposed between the nuclear membrane and the nuclear sub-
stance, thereby inducing the formation of one or numerous nucleoli.
ec. The invasion of the nuclear cavity by a nourishing protoplasmic
reticulum, which traverses the pores of the membrane and crosses
the space occupied by the nuclear sap.”
“ Nuclear substance ” is, like protoplasm, capable of automatic motion, which
may be either irregular (amceboid) or executed in a remarkably uniform man-
ner, as during cell division ; but in other points — especially in its deportment
with acids and with carmine and hematoxylin staining fluids —it shows con-
stant differences from cell protoplasm. It is not maintained that “ nuclear
substance” is everywhere the same, any more than that cell protoplasm is
identical in chemical composition in all cells. For the “nuclear sap” specific
properties, which would allow it to be recognized as a thing sut generis, have
not yet been established.
Often a portion of the nuclear substance remains in the periphery of the
nucleus, thus forming a spherical mantle of homogeneous substance exhibiting
the same chemical reactions as the nucleolus. This cortical layer of the nu-
cleus (Kernrindenschicht) should not, in Hertwig’s opinion, be confounded
as has often been the case heretofore, with the nuclear membrane, which is a
superimposed structure (Auflagerung), whether derived from the nucleus or
from the protoplasm is unknown. The “ Kernrindenschicht” is related to the
“Kernmembran ” much as the cortical layer of the protoplasm of the cell is
related to the cell membrane, and like the last-mentioned structure the nuclear
membrane is functionally a protective organ, since it cuts off the nucleus in its
wet
¥
264 BULLETIN OF THE
quiescent state from the influence of changes in the surrounding protoplasm.
The nuclear membrane and the “ Protoplasmanetz”’ are functionally correlated,
inasmuch as the nutrition of the nucleus, which is impeded by the former, is
facilitated by the latter. This view agrees with the fact that both structures
are limited to extensively differentiated nuclei.
SPENGEL (’76, p. 31, Taf. IT. Figs. 33, 35) calls attention in his paper on the
Urogenital System of Amphibia to a peculiar star-like figure which is occa-
sionally found to take the place of a nucleus in cells from the testis of Cecilia
rostrata. The “Stabchen” of this figure are stained in the hematoxylin as
intensely as the nucleolus in other cases. Spengel thinks this appearance com-
parable with the process of nuclear division. Other structures, in form similar
to Chinese characters, are often found in nearly all of certain groups or balls of
testis cells.*
FLEMMING (’76) has communicated, in a paper devoted exclusively to the con-
sideration of the nature of the nucleus, the results of studies undertaken with a
view to determining whether the intranuclear network was present as a struc-
ture intra vitam. He made use of the urinary bladder of the salamander, and
operated on animals that had been poisoned by the injection of a solution of
curare, as well as on those which were not curarized. In both cases the tissues
remained in the same condition.
With proper illumination it was possible to discern in endothelium, in mus-
cular fibres, in cells of connective tissue (Bindesubstanzzellen), and in nerve-
cells, this delicate intranuclear trestle-work; but only in a few,eases can its
connection with the nuclear wall be traced on all sides. The appearance is
often so blurred that one might, without exercising great care, be led to a be-
lief in the existence of only a granulation of the nucleus; the apparent granules,
however, are the optical cross-sections of the fibres of the continuous network.
Besides these apparent granules, there are present from one to three large nu-
cleolar structures, “ Hauptnucleolen,” and often smaller nucleoli, “ Neben-
nucleolen,” which differ from optical sections of the network in which they lie
by their greater size and different coloration or refractive power. In many of
the nuclei nothing of all this can be seen, but the results obtained by the use of
reagents are proof that, in these cases also, the same structure is not wanting.
_ By Hermann’s method of analine staining still other structural differentia-
tions than those already mentioned may be demonstrated, — “ Analinflecke.”
These “ Analinflecke” are not discrete corpuscles, but more intensely stained
portions of the network; apparently they are only in part identical with the
nucleoli before mentioned, as they are far more numerous than the latter.
In the discussion of the question, as to whether these appearances are due to
* Perhaps the latter are of the same nature as the remarkable modifications which
the nucleus undergoes in certain cells of many invertebrates, especially Arthropods.
Compare in-this connection the following: H. Meckel (’46, pp. 33, 44, Taf. II. Figs.
26, 32, 38); Leuckart (Frey u. Leuckart, ’47, p. 61, foot-note); Leydig (’57, p. 18,
Fig. 8);-Chun (76, p. 47, Taf. I. Fig. 5); Helm (’76, pp. 444, 458, Figs. 1-18,
55, etc.); and P. Mayer (78, p. 42, Taf. I. Figs. 6, 9, 10, LL)
een
8 2
MUSEUM OF COMPARATIVE’ ZOOLOGY. 265
coagulation, to artificial and post-mortem influences, or are present as struc-
tural features of living nuclei, Flemming offers the following reasons for regard-
ing the former supposition as improbable : —
1. The regular form and arrangement of the network, which varies, it is
true, with the use of different reagents, but within very narrow limits.
2. The constancy with which the nucleoli are found in the fibres (Balken)
of the network.
3. The différentiations shown by the aniline staining to exist in the substance
of the network, which would be homogeneous were the network only a result
of coagulation.
“The network,” Flemming therefore concludes, “ is the expression of a given
structural condition of the nucleus.”
Although finding the network very distinct in fresh sections of hyaline carti-
lage from the salamander, and thus being able to confirm Heitzmann’s discov-
ery of the nuclear network in the cartilage of higher vertebrates, our author is
unable to convince himself, from the study of epithelial cells, that. the extra-
and the intra-nuclear network are continuous, but states, on the contrary, that
the network of the plasma and that of the nucleus deport themselves quite
differently under the influence of the same chemical reagents. Flemming takes
exception to some points in R. Hertwig’s conception of the nucleus. He be-
lieves his present paper is sufficient proof that the intranuclear network is not
limited to highly differentiated cells; and neither indorses its supposed nutri-
tive function nor is able to find evidence that it comes from the protoplasm
of the cell,—the less able since he finds no trace of pores in the nuclear
membrane.
According to Lavpowsky (’76, p. 525, Taf. XX XV. Fig. 19. 1, 2, and 3), the
ganglionic elements of the ganglion spirale often exhibit about the nucleolus
the circle of granules described by Eimer.
ARNDT (’76), the substance of whose paper I know only through Schwalbe’s
abstract in Hofmann u. Schwalbe’s Jahresbericht, etc. (Bd. V., Anat., p. 25),
considers the cell nucleus as composed of a homogeneous semi-solid “ Grund-
substanz” and imbedded “ Elementarkiigelchen,” each of the latter consisting
of a capsule and a contained dark corpuscle. The “ Grundsubstanz” is ar-
ranged throughout in the form of a network in whose interstices the “ Ele-
mentarkigelchen ” lie.
In the human decidua serotina examined in warm, fresh serum, one finds,
according to LANGHANS (’76), that the nuclei are without trace of nucleoli or
granules, — homogeneous, lustrous, and with even outline. With the use of
reagents there promptly occurs (and in any event after the lapse of some time)
a separation of its substance — either throughout the whole nucleus at once, or
else beginning first at the periphery — into a highly refracting and a feebly re-
fracting portion. The latter collects into numerous small, round, closely packed
vacuoles. The former, the “septa,” are at first of uniform thickness and very
delicate. The vacuoles become larger and the septa break through at first near
the periphery. Finally the whole nuclear substance (“Kernsubstanz’’) is
Q
266 BULLETIN OF THE
grouped into nuclear membrane, and 1-3 dark-outlined nucleoli. All the rest
is a water-clear “ Kernsaft.” In the author’s opinion the whole process is a
“post-mortem disintegration.”
TOROK (’77) * has observed in living Eph cells of embryos of Siredon
that the “ Dotterplittchen ” suddenly change position, and that this locomotion
is more precise in proportion as the nucleus is more sharply differentiated. No
immediate relation exists between this phenomenon and changes of form on
the part either of the cell or its nucleus, inasmuch as the latter are not accom-
panied by any rearrangement of the yolk elements. It is concluded from the
study of osmic acid preparations that such Dotterplattchen movements re-
sult : (1.) Either in a group (or groups) of Dotterplattchen which melt together
more or less completely and give rise to a network ball (kugelformige Netzge-
bilde) which may occupy the same cell with one or several nuclei, or may take
the place of a nucleus. (!) This reticular structure is succeeded by fine fila-
ments having an irregular course, but the whole is not of the nature of a
permanent differentiation, and eventually disappears. Or (2.) in a radiate
arrangement of the Dotterplattchen about a centre of unknown significance.
This is succeeded by a grouping of the same elements into a circle. With
the widening of the circle there appear, as a differentiation of the central
ends of the Dotterplittchen (possibly with the participation of the homo-
geneous protoplasm), radial rods lengthening ultimately into fibres with an
increasing tendency to become curved (Stabchen-Faden). The Dotter-
plattchen disappear, and thus the whole cell loses its original character.
Both these structures are only transitional manifestations of cells in process of
becoming tissues, and the “ Stibchen-Faden ” disappear earlier (in the embry-
onic life of the Siredon) than the “ Netzgebilde.”
It is perhaps attributable to his firm belief in the total disappearance of the
germinative vesicle and ina like fate for the nucleus of embryonic cells, that
Torok failed to connect these remarkable changes with the process of cell
division (to which they so clearly belong), rather than with that of the
differentiation of cells into tissues. Yet it did not escape him that the dis-
appearance of the nucleus was accompanied with similar transpositions of the
“ Dotterplittchen,” only he maintains that in many cases they are independent
of each other, so that, while in one cell new formative centres arise in the
presence of a well-preserved nucleus, in another cell no trace of a nucleus of
whatever kind is to be found.
Of the changes in the nucleus, starting from the well-formed structure, Torok
says that a finely granular condition is followed by the appearance of coarser
eranules and an increasing transparency of the “ Zwischensubstanz,” accom-
panied by an increase of the mass of the nucleus. Then the coarse grains
* See also Torok, "74.
+ That new centres of attraction arise before a perceptible change takes place in
the nucleus is conclusively shown in the present paper, and has also been pointed out
by Strasburger (’'76, p. 158) for Isoétes.
MUSEUM OF COMPARATIVE ZOOLOGY. 267
are differentiated into rods, which are soon drawn together by a contrac-
tion of the Zwischensubstanz, lose their sharp outline, become irregularly
curved, and so joined together that there results an indefinite network of
coarser distinct, and of finer blurred fibres. This network is the typical form
of the highest differentiation of the nucleus, which may vary in the fineness
of its fibres and the closeness of its meshes in cells from different embryonic
stages.
Often cells are to be found in which, by the side of one or two existing
nuclei, two, three, or even four new nuclei may arise; and their development
may be traced. (!) New nuclei may arise by a process of formative differentia-
tion from the Dotterplittchen. Neither cell nor nucleus has always the same
signification. A nucleus may later attain the dignity of a cell.
The studies of Térék can hardly be considered as convincing proof that the
prevailing histological notions are altogether out of joint. Few, 1 suspect, will
be inclined to admit so prominent and active a réle for the Dotterplattchen,
even in those objects which form the basis of Tordk’s studies, to say nothing
of the cases where such “ Formelemente” (e. g. Cucullanus) are wanting. It
is not easy to understand why the sudden rearrangement of the yolk elements
into a radial position is necessarily to be referred to the yolk particles them-
selves as the efficient living substance, rather than to the homogeneous matrix
in which they lie. The proof of this assumed explanation appears to be en-
tirely wanting.
That the changes described — certainly the “Stabchen-Faden” —are phases
of nuclear division can hardly be doubted. Fig. 11 is particularly strik-
ing in comparison with the amphiasters of segmentation, and many of the
other figures are readily comparable with stages of division which have been
so exquisitely figured by Flemming in his last paper (’78°).
In arecent communication, Eimer (’77) defends his previous papers from
the charge of representing artificially produced conditions of the nucleus. The
“clear area” receives the name of “hyaloid,”’ and the “circle of granules”
separating it from the peripheral portions of the nucleus is now called
“shell of granules” (Kornchenschale), as expressing more accurately the
spatial distribution of the granules. Stimulated to renewed studies of nuclei
by the work of Heitzmann and Flemming, Eimer finds occasion to extend
somewhat the nature of his earlier conclusions respecting the structure of
nuclei, inasmuch as he finds that very generally the granules of his “‘ K6rnchen-
schale” are connected, each by a delicate radiating filament which traverses the
“hyaloid,” with the nucleolus, a clear indication of this arrangement having
been already figured by him (73, Taf. VIII. Fig. 82.6) in his Beroe studies.
Further than this, Eimer corroborates the view that the nucleus consists of a
hyaline “Grundsubstanz” traversed by protoplasmic filaments. Outside the
“Kornchenschale ” these filaments form a network of narrow meshes, which
has usually been mistaken for a granular structure, but within that “shell”
only the radial fibres are met with. The latter —and of course the “ granules ”
— are nearly constant in number, so that about nine are in the field of vision
268 \ “SS BULLETIN. OF THE
when the ‘centre ‘of the nucleolus is in focus! The’ granules of the: Korn-
chenschale”’ are separated from the surrounding network by a homogeneous
space, so that a direct connection between the network and ‘ Kérnchenschale”
cannot be made out except in rare cases, as when the granules are hardly dis-
tinguishable from those of the network. In such cases the granules of the
“shell” are also directly united to each other by filaments.
An exceedingly fine protoplasmic network in the body of the cell (ciliate epi-
thelium) is in connection on the one hand with the cilia, and on the other hand
sometimes (gills of Axolotl) appears to be in continuation with the nuclear net-
work (p. 116). The objects which Eimer has figured are principally ciliaté epi-
thelium from the mouth of Salamandra, the gills of Siredon and Anodonta,
and certain ectoderm cells of Trachymeduse. The first glance at some of the
figures is enough to raise at once the question, if these appearances are not
really due to phases of nuclear division ; or, to be more exact, if the “ Kérn-
chenkreis”. is not after.all identical with the well-known “ Kernplatte.” The
possibility of such an equivalency has not escaped Eimer himself (p. 111), but
an attempt to explain -how the “ Kornchenschale”? may be harmonized with
the “Kernplatte,? and the radial ‘fibres with. the spindle fibres; is mot: made;
and there are many reasons to interfere with the. establishment:ofisuch ascomx
parison. If Eimer’s descriptions permitted one to,.suppose that the granules
of his “ Kérnchenkrets” were limited to a single plane,.as that name naturally
implies, an important objection would be cancelled ; but they do not. If it
were permitted to suppose — which it is not—that the central nucleolus did
not occupy the same plane as the granules of the “ Kérnchenkreis,” one might
identify the radial fibres of Eimer’s description with the “projected” spindle
fibres, and his “nucleolus” with one of the poles of the spindle. Further,
such an identification would necessarily compel its extension to those wheel-
and-spoke figures, several of which are represented as occurring in a single
nucleus (see Figs. 6, 9, and 10, op. ctt.). Iam unable to recall a parallel case
of multiple spindles to place beside it. Perhaps the very recent studies of
Flemming (’78°) will be sufficient to make more intelligible the relation of
“ Kornchenschale ” and “ Kernplatte.”
In a note FLEMMING (’77) communicates the fact that he has observed the
nucleoli and the nuclear network, previously described by him, in the hwing
and uninjured larve of salamanders, so that the inference possibly to be drawn
from the studies of Langhans, viz. that these phenomena are all post-mortem,
is in no way justified. These conditions were observed on nuclei of connective
tissue in the tail, the nuclei of nerve cells, nuclei of red blood corpuscles,
etc. In the living condition, however, the structure is pale, and only to be
seen with good light, a fact that may explain the account of Langhans. More-
over, the use of reagents may produce shrivelling and coagulation ; neverthe-
less, the substantial identity of the fresh and hardened conditions cannot be
called in question.
SrricKER (’77) not only recognizes the existence of a reticulum in the nu-
cleus, but has directly observed an amceboid motion of its filaments which he
MUSEUM OF COMPARATIVE ZOOLOGY. 269
regards as protoplasmic. He considers the cell nucleus as nothing more
than an encapsuled portion of the active cell protoplasm, which may on occa-
sion become free by a rupturing of the capsule into two or more pieces. He
has observed, for instance, that in certain colorless blood corpuscles of Triton
and the frog the nuclear envelope becomes broken through, and the intranuclear
network and the cell protoplasm are thereby apparently in direct continuation.
“The ruptured capsule rests on an amoeboid mass (nuclear contents), like a
snail shell on a crawling snail.” In the case of naked, for the most part un-
changeable, nuclei from the blood of the frog, Stricker adopts the term “ Kern-
substanz” for the envelope and network of the nucleus (since they appear to be
alike), and “ Kernsaft” for the clearer mass which fills the interstices of the
network. These naked nuclei are, however, genetically connected with uni-
nuclear cells, inasmuch as the latter are seen to change in a manner which
permits no other assumption than that the protoplasmic zone has withdrawn
within the nuclear envelope. The retiring protrusions become smaller, and
finally the nucleus appears naked. The protoplasmic filaments often break
forth afresh, and the whole is again in motion. On such naked nuclei repeated
attempts at division were observed. From all this it is to be concluded that
the free nucleus with active (beweglich) internal network is only “ein abge-
Kapselter Zellleib,” and that the capsule is perforated or permeable.
In the blood of Triton and the frog there are still other elements, — finely
granular, “ sehr beweglichen,” colorless blood corpuscles. In these the nuclei
are not constant structures ; they appear and disappear, and again are formed
in the cell out of components of the cell body. The nuclear membrane is
only a transitory formation, like the waves on water. While one portion of
the nuclear membrane becomes invisible, a neighboring zone of the protoplasm
is compacted (new nuclear membrane) ; the nucleus has thus become larger or
smaller according to the position of this zone. The nuclei of these blood cor-
puscles, then, are not persistent formal elements. F
The nuclei of the tissue cells, or fixed cells, are less changeable, but even
here the network is sometimes (ciliate cells from the frog’s palate) amceboid, and
the nuclear membrane may change form, though it is not known to disappear.
“ Als Merkmal der fixen Zelle mag der Kern noch von Bedeutung sein; als
ein nothwendiges Merkmal der beweglichen Zelle kann ich die Existenz eines
formell abgegrenzten Kerns nicht mehr anerkennen.”
The optical effect of the reticulum in the living nucleus is quite other than
that in the dead nucleus. In the latter one may speak of a “nuclear sub-
stance” and a “nuclear sap.” In the living nucleus there must be, just as in
the cell, an intranuclear fluid in the form of very small vacuoles ; but it is not
to be considered that the fibres of the net-work are bathed in the living cell by
a “nuclear sap.” The effect, on the contrary, is the same as though the reticu-
lum were produced by a special arrangement of the living material, —as it
Were by an unequally distributed density of that substance.
) Stricker considers as most important his observation of the disappearance and
Teappearance of the nucleus (active blood-corpuscles), and finds particular assur-
270 BULLETIN OF THE
ance of the accuracy of his position in the fact that he has “directly seen how a part
of the nuclear membrane assumes the character of the rest of the cell body, whereby
the contents of the nucleus become one with this cell body.” This would cer-—
tainly be most important were it sufficiently established by Stricker’s observa-
tions. It occurs to me, however, that the derect optical properties of the living
protoplasm and nuclear membrane afford only one out of many criteria by
which to judge of the identity of the two substances,
It were as competent to say of two fluids, that, because both are clear and of
like refractive properties, consequently they are identical. It will be soon
enough to accept Stricker’s conclusions when it shall have been shown that no
reagents are’ capable of disclosing a difference between the two substances of
these cells during the stages of which he speaks.
ARNOLD (’78, p. 131, cf. also pp. 138, 139, and Taf. II. Fig. 1) affirms with
some reservation the existence of deeply colored granules and filaments in the
substance of the cell and nucleus of cartilage taken from animals, into whose
blood indigo-carmine (sulphoindigotate of soda) had been infused.
KLEIN’S (’78) studies on the newt (Triton cristatus) were mostly conducted
by the use of a 5 % solution of chromate of ammonia, followed by staining
in carmine, picrocarmine, or hematoxylin. His results —so far as regards the
structure of the nuclei—are very uniform for a variety of tissues, viz. epi-
thelial cells of the stomach and the various components of the mesentery,
surface endothelium, unstriped muscle fibres, connective-tissue corpuscles, —
both migratory and fixed, — blood capillaries and lymphatics, and especially
nucleated endothelial plates investing the nerve fibres. An extremely beautiful
network of fibrils permeates uniformly the interior of all the epithelial nuclei,
“intranuclear network.” The nuclear membrane is always well defined, and
in some instances the network does not extend quite up to it, leaving an un-
occupied zone. But inall cases the network is in connection with what is
known as the limiting membrane by numerous fibrils.” How these fibrils
differ from the fibrils of the network is not stated, nor why they are not an
integral part of the network. The following description of the nuclear mem-
brane seems to obliterate the distinction which was so clearly implied ; “ What
usually appears as nuclear membrane is composed of an outer thicker portion,
which is the limiting membrane proper, and — closely connected with it —of
an inner more or less incomplete — probably because reticular — delicate layer,
which is, properly speaking, a peripheral condensation of the intranuclear net-
work, with which it is, of course, connected by longer or shorter threads. The
clear space which may be observed in some instances between the ‘membrane’
of the nucleus and the intranuclear network is due . . . to a retraction of the
latter from the former, and is a space, not between the two layers of the limit-
ing membrane, but between the inner layer of this and the bulk of the intra-
nuclear network.” ;
The fibrils of the network are highly refractive, and vary in thickness,
course, and arrangement. Almost always minute bright spots — more numer-
ous in dense or shrunk networks = are to be seen ; they are points of anastomo-
MUSEUM OF COMPARATIVE ZOOLOGY. AN
sis for the fibrils, or their optical cross-sections ; moreover, some fibrils possess
irregular thickenings. Nuclei examined in a perfectly fresh condition, with
favorable light and powerful objectives (e. g. Hartnack, Imm. 10), show distinct-
ly, although faintly, part of the intranuclear network. Klein disagrees with
Flemming when the latter finds ground for believing in'the existence of nucle-
oli fundamentally differing from the granules which are referable to thicken-
ings in the network., At best, the so-called nucleoli are due to a shrivelling
and intimate fusion of a part of the network, and are only transitory ap-
pearances. In the fresh condition it is demonstrable that the nucleoli are
“accumulations of the fibrils of the network.”
An intracellular network is also conspicuous in most of the cells studied. In
epithelial cells that have retained their cilia, the latter are seen to pass into the
cell substance and identify themselves with the intracellular network, the fibrils
of which in turn are in direct connection with the intranuclear network.
“Tn all muscle fibres the intranuclear fibrils may be traced to emerge as a
bundle from the pole of the nucleus, and to become identified with the bundle
of fibrils representing the core of the muscle-fibre itself.” The nucleus pos-
sesses a small circular hole at each pole through which these fibrils emerge.
Klein says that, after giving the point the greatest attention, he has been unable
to find any evidence of a connection between the axis cylinder of nerve fibres
and the intranuclear network ; on the contrary, he is able in most instances to
follow the axis cylinder along one side of the nucleus beyond the latter. This
he thinks is the normal relation of the axis cylinder to the intranuclear
network.
FLEMMING (’78°) publishes in a preliminary paper some of the results of
studies conducted on the simple plan of choosing for examination such objects
as permit a comparison of the living cells with stained preparations of the
same. Numerous tissues, especially of the salamander, are made the objects
of study, and the phenomena carefully reproduced in numerous figures.
The first of the two main divisions of the paper treats of the structure of
the quiescent nucleus ; the second, of cell division in growing and in inflamed
‘issues. The quiescent nucleus examined in the living condition exhibits a
network which, however, varies in different cases, and is not so regular as often
portrayed. The various appearances produced by the use of reagents — which
vary in the reliability of the results produced — undoubtedly find their expla-
nation in the existence of a corresponding structural differentiation in the
living nucleus, but how far the intranuclear structures which appear after
ireatment with acids are identical with the living condition, cannot be so read-
ly determined. Even with the best preservative reagents there is more or less
listortion. The fine granulation of chromic acid preparations is held to be
lue to coagulation, as are possibly some of the smaller fibres of the network,
out certainly not all. The effect of the chromates is especially untrustworthy.
) The results touching the nature of the quiescent nucleus are summarized
by the author himself much as in a previous paper (Flemming, ’78). The
(wiescent nucleus consists of, —
I
272 BULLETIN OF THE
(1.) A mural layer (Wandschicht), — the “nuclear membrane.”
(2.) A substance distributed through its interior, connecting with the mural
layer, and disposed in branching fibres, which do not exhibit any distinct reg-
ularity of arrangement (nuclear net, intranuclear network, or, better still,
imtranuclear tressel). The fibres (Balken) of this tressel present thickenings
of variable form and number, — reticular nodes (Netzknoten).
(3.) Genuine nucleoli, which lie usually in the thicker, occasionally in the
thinner, fibres of the network from which their substance differs. In the living:
condition the nucleoli— often several, but generally only one or oe
frequently not distinguishable.
(4.) A pale substance, which fills out the remaining intermediary space,
and exhibits in the living condition no structure : — Zwischensubstanz of the
nucleus.
Flemming especially insists upon the point that the nucleols are not simply
thickenings of the tressel-work, and defends his position by the results obtained
in staining and decolorizing. It may be observed, however, that the process
of decolorizing would necessarily take substantially the course indicated, even
if the nucleoli were only concentrations of the tressel-work, since the removal
of coloring matter must, ceteris paribus, permit the bulkier portions of the
structure to remain longest in view. But this objection is anticipated by the
author when he emphasizes the fact that the Netzknoten (inclusive of nucleoli)
are often more intensely stained than their connecting fibres. “ Die Netz-
knoten sind vielfach absolut, nicht bloss relativ nach threr Grésse, starker
gefarbt wie die tibrigen Theile des Netzes.” But the very fact that the
Netzknoten stain intensely seems to me very unfavorable for the demonstra-
tion of a difference between the nucleoli and the tressel-work, for the
Netzknoten are defined to be simply thickenings of the tressel-work.
Other conclusions from the results of staining are, that, since the nucleus is
alone stained, or at least more deeply than the rest of the cell, it must be dif-
ferent from the remaining substance of the cell, —therefore different from
“protoplasm.” The staining of the nucleus affects all its parts, but the inter-
mediary substance less than either the network, its nodes, or the mural layer.
In well-stained preparations the external limit of the nucleus is sharply
marked, so that a connection of intra- and extra-nuclear fibres is doubtful.
Flemming finds nothing to support the idea that the nucleus deports itself
in staining like the plasm of colorless blood-corpuscles or young cells.
c. THE NUCLEUS DURING DIVISION.
Introductory.
As ig well known, two fundamentally different views have been held
about the condition of the nucleus at the time of cell division. Accord-
ing to one, the nucleus, on account of its dissolution and the distribu
tion of its substance through the common protoplasm, disappears before
MUSEUM OF COMPARATIVE ZOOLOGY. 273
each division of the protoplasm of the cell, and the nuclei of the daughter
cells arise as quite new structures; according to the other view, the
nucleus of the parent cell gives origin directly to the new nuclei by a
process of division, and the cases of supposed disappearance are to be
explained as resulting simply from a temporary obscuration of the
nucleus.
How firmly established the former view was with botanists in 1874,
‘may be readily gathered from Sacus (Lehrbuch der Botanik, 4° Auf-
lage, Leipzig, 1874, pp. 18, 19), who expresses his doubt about the
division of the nucleus being in any way a general phenomenon.*
Doubtless an equally true reflection of the views prevailing at the
same time among zodlogists is presented by GrcrenBaurR (’74, p. 17)
when he says: “ The division is introduced by a division of the nucleus,
and as a rule it can be established that the individual phases of the
division of the nucleus precede the corresponding stages of division in
the cell. In many cases, however, there appears to be a new formation
of the nucleus.”
From a comparison of these citations two conclusions can be drawn:
first, that in both “‘kingdoms,” as recently as 1874, two radically differ-
ent methods of deportment were admitted for the nucleus; and secondly,
that opinions were still at such variance as to allow very little room for
a parallelism between plants and animals in regard to the persistence of
the nucleus during cell division.
Aside from the disappearance of the old nucleus, it was the increase
in the size of the new nuclei from very small beginnings, which seemed
to entitle the idea of complete nuclear dissolution to consideration at the
hands of zodlogists.
Of modes of cell formation other than by division, zodlogists very gen-
erally accepted as well grounded a process of budding, in which the di-
vision of the nucleus into numerous new nuclei was followed by a
simultaneous constriction of the protoplasm into a corresponding num-
ber of parts (compare Meissner, ’54%, p. 262); but a so-called endo-
genous cell production — the equivalent of the “free cell formation”
of the botanists — has not shared with zodlogists the same confidence.
In the earlier accounts of cell division, the formation of a partition (or,
more commonly, the lengthening and constriction of the nucleus) was
observed to accomplish its division. The presence of two approximated
* “Tass iibrigens das von Hanstein (Sitzb. der niederrhein. Gesellsch., Bonn,
1870) beobachtete Verhalten der Kerne nicht ganz allgemein ist, zeigen schon die
Theilungsvorginge in den Antheridien der Charen u. s. w.”
VOL. VI.— No. 12. 18
274 BULLETIN OF THE
nuclei in a cell with undivided protoplasm has sometimes furnished the
basis for an inference that an actual division had taken place. Yet the
most accurate, connected, and careful of these observations failed to
disclose what improved means of investigation have shown to be of very
general occurrence.
One thing, however, especially in the case of segmentation, had been
very often recognized in the best observations ; namely, that the nucleus
about to divide was a homogeneous body, exhibiting neither membrane
nor nucleolus, and often that its outline became quite indistinct.
Among the papers which take notice of this interesting peculiarity
are the following.
In 1846 the attention of Von Bazr (46, pp. 36, 37) was attracted by
the appearance of a “ langgezogener heller Schein” in the eggs of Echi-
nus soon after fecundation, and also before each segmentation of the
yolk. At p. 39 he describes more in detail the condition of the mature
ego: “Im reifen Ei des Seeigels erkannte man an einer Stelle seiner
Oberflaiche einen hellen Kreis, der etwa ein Achtel vom Durchmesser
des ganzen Kies hatte. ... Dass es nicht ein Blaschen oder eine Zelle,
sondern ein sehr weicher Korper ist, was dusserlich als heller Kreis
erscheint, glaube ich nach vielfaltigen Versuchen, die ich mit mechani-
schen Zertheilungen und einigen Reagentien anstellte, mit bestimmtheit —
erkannt zu haben, obgleich dieser Korper bald in seiner Metamorphose
vollig durchsichtig wird.”
Lovin (48, p. 545), describing the development of Modiolaria and Car-
dium, says that “the nuclei of the cleavage spheres have no nucleoli,
and behave under the compressorium in no way like vesicles or cells.
They appear to be solid, but of quite limited consistence. Their peri-
odical disappearance can hardly escape observation, but it is more diffi-
cult to make out how this happens.”
As we have already seen, Warneck was certainly one of the first to
point out the peculiar modifications which the nucleus suffers before
its constriction and division. He was even impelled — probably in part
from the small size of the new nuclei when they first became visible as
distinctly outlined structures — to the conclusion that the nucleus un-
derwent actual diminution of volume during each act of division, without,
however, losing its identity.
J. Miitier (52%, pp. 16, 17) speaks of “das Keimblischen oder der
helle Kern,” and states that it contains no germinative dot; and in the
communication published in his Archiv (52, pp. 11, 19) he expresses
even more clearly this peculiarity. ‘Das Keimblischen im reifen Et
MUSEUM OF COMPARATIVE ZOOLOGY. 275
von Entoconcha ist vollig hell und hat eine einfache nicht doppelte
scharfe Contour. In seinem Innern sind keine Granula und nichts
einem Keimfleck Aehnliches zu erkennen, es ist durch und durch so ziihe,
dass man an der Existenz einer Membran zweifeln koénnte. . . . Das Keim-
blaschen . . . gleicht daher mehr dem, was Von Baer in den reiferen Eiern
des Seeigels den Kern des Eies nennt.” )
Leypie (’54, p. 28) especially makes clear this feature, when, in de-
scribing the segmentation of the eggs of a Rotifer (Notommata), he
speaks of “der homogene helle Kern des reifen Kies — das Keimblaschen
—u.s. w.,” and (p. 102) “das Keimblaschen im reifen Ei — welches
iibrigens keinen Keimfleck mehr hat, auch nicht ein Blaschen, sondern
ein homogener ziiher Korper ist.”
Merscunikorr (66, pp. 410, 411) affirms that in Miastor, after the
“ Keimfleck” has disappeared, the germinative vesicle divides into two
nuclei of equal size. For Aphis the absence of the germinative dot also
characterizes the nucleus before division (p. 438). In Nemertes, also,
a very brief notice of the mature egg is given by Metschnikoff (’69%,
p. 50, Taf. IX. B, Fig. 1, vg.), in which he mentions the germinative
vesicle as being large and transparent, but of an irregular form.
Ep. vAN BENEDEN (’70, p. 39), although he znfers (p. 31) that the
division of the nucleolus precedes the division of the nucleus, and this
in turn precedes that of the “germinative cell” in the case of Distoma
cygnoides, admits (p. 39) that in Udonella the nucleus, which the “ ger-
minative cell” embraces and which represents the germinative vesicle
[first segmentation nucleus], no longer has a clearly recognizable contour ;
it still remains, however, as a paler spot. In the mammalian egg, too,
the same peculiarity of the nuclei of cleavage spheres is to be inferred,
inasmuch as, according to Van Beneden (p. 179), ‘La vésicule germina-
tive se conduit dans l’ceuf absolument comme les noyaux dans les sphéres
de segmentation” ; and (p. 174), “Il est incontestable aussi qu’ & certains
moments la vésicule germinative devient trés-peu distincte et qu’il sou-
vent impossible de la distinguer.”
The division of blastodermic cells in Tegnaria domestica has been de-
scribed by Baupiani (73, pp. 51, 52, and Figs. 64-66), and the deport-
ment of the nucleus observed. ‘On voit d’abord le nucleus, de pale et
circulaire qu’il était, prendre une forme allongée et devenir plus réfrin-
gent.” It is only the internal substance of the nucleus which divides at
first ; the more elastic enveloping membrane continues to hold these
halves together for some time (see his Figs. 65 and 66). This connecting
band, which Balbiani thinks to be the nuclear membrane, is unquestion-
276 BULLETIN OF THE
ably the band of interzonal filaments, but the author failed to discover
that it was composed of filaments, and in general overlooked all the finer
details of structure which the use of reagents would have made apparent.
- But these are enough to show how frequently had been noticed a
change in the appearance of the nucleus before segmentation. Aside, °
however, from this peculiarity and the almost concurrent testimony as
to a lengthening of the nucleus by those who believed in its division, '
little advance was made in a knowledge of the nuclear changes.
a. Segmentation. — The peculiar metamorphoses which the substance
of the nucleus undergoes in the formation of the spindle figure, and the
accompanying changes which manifest themselves in the surrounding
protoplasm of the yolk just prior to cleavage, like most discoveries, have
been only gradually comprehended. Yet the advances in the intimate
knowledge of these changes within the last half-decade seem marvellous.
In the light of recent studies on maturation and impregnation, we
are now able to say that most of the earlier descriptions of the lengthen-
ing, constriction, and ultimate division of the nuclear structure of the
egg just before the first segmentation rest upon the observation of some-
thing else than the germinative vesicle. In most cases it has been either
the nucleus or the amphiaster of the jirst cleavage sphere that has been
seen and wrongly considered as the dividing germinative vesicle. The
class of observations in question, then, deals not with the phenomena of
maturation, but with those of cell division, and is therefore properly
considered in this connection. But where, on the other hand, observa-
tions have been less connected, and a division has been inferred from the
presence and close approximation of two nuclear structures, it may be
that in some cases the pronuclec have been mistaken for the resultants
of division. Such is probably the case, to cite a single example, with
the observations of Kolliker (43, pp. 77, 78, Taf. VI. Figs. 5, 6) on
Ascaris dentata.
Of those who have seen something more than an elongation of the
nuclear structure, it seems that among zodlogists Ratzel was the earliest ;
but as his observations probably relate to the germinative vesicle rather
than to the primary cleavage nucleus, they will be considered under the
head of “ Maturation.”
Another observer, who has given evidence of having seen in animal
cells the structure which is now generally known under the name of
“nuclear spindle,” is the Russian embryologist, Kowatevsky (’71, p. 13).
As is well known, this naturalist early made use of sections in his em-
bryological studies of invertebrates. The first unequivocal view of the
”
MUSEUM OF COMPARATIVE ZOOLOGY. QT7
fibrous nature of the structure in question is due to this method of in-
vestigation. In tracing the development of the oligochetous worm
Euaxes, it was discovered that the formation of new cells by segmenta-
tion was accompanied by a peculiar modification of the “nucleolus.”
This is described for the stage in which the embryo consists of only four
cells as follows: ‘‘The section [Taf. IV. Fig. 24] passes through the two
small spheres e and c, and one sees that from these two spheres there
are beginning to be formed two new smaller ones, in the composition of
which the halves of the nucleoli and a small portion of the whole seg-
mentation sphere take part. The nucleolus does not appear in the sec-
tions as a vesicle in process of division, but exhibits, in the old as also in
the newly forming cell, two granular accumulations, which are united to
each other by means of fine, granular, but very evident protoplasmic (?)
fibres [Strange ].”
There can be no doubt, on examination of the figure, that the so-called
granular accumulations are identical with the lateral zones of thicken-
ings, and that the Strange uniting them are the interzonal filaments.
The former are represented as lying in two parallel planes, appearing
consequently in the form of two parallel straight rows of prominent
granules ; the latter, as faint lines of much smaller granules, which are
parallel or slightly convergent toward the granular accumulations which
pertain to the smaller cell. No curvature is shown in these fibres, nor
is there any indication of their continuation beyond the two lateral zones.
The latter are so far apart that the one belonging to the larger cell lies
quite near the centre of the spherical mass of protoplasm which the author
leaves one to infer is the nucleus of the larger cell, but which unques-
tionably is that portion of yolk protoplasm* which is destitute of coarse
granules, and which is so often seen to present a radiate appearance.
Such were the shadowy glimpses that had been caught of the nucleus
in its metamorphosis, when, about the beginning of 1874, there appeared,
independently of each other, four articles upon representatives of three
of the main groups of invertebrates, — cclenterates, worms, and mol-
lusks, — each of which devoted considerable attention to the changes in
the nucleus before segmentation, and especially to the stellate figures
which hitherto had failed to attract much attention or to elicit theoreti-
cal notions as to their significance.t
* Biitschli (76, p. 398) has already called attention to this as being the first ob-
servation on the nuclear spindle, and has also pointed out the incompleteness of
Kowalevsky’s knowledge of this structure, and its relation to the nucleus.
t From this point forward the two phenomena, spindle and stellar figures, may
be considered together as internal changes of the cell during division.
278 BULLETIN OF THE
Not being able to gain access to SCHNEIDER'S paper (73) on Mesos-
tomum, I am indebted to the citation in Biitschli me) p. 399) for the
synopsis which follows.
In the fecundated summer egg first the outline of the nucleus, which
Schneider holds to be the original germinative vesicle, [apparently]*
disappears, the nucleolus alone remaining visible. Acetic acid, how-
ever, brings out the much bent and folded ontline of the nucleus.
Finally the nucleolus disappears, and the whole nucleus is converted
into a mass of finely curled fibres (Faden), which become apparent
[only] upon application of acetic acid. In place of these thin fibres
thick cords (Strange) finally appear, at first irregularly, afterwards ar-
ranged in a rosette which lies in a plane (equatorial) passing through
the centre of the sphere. These cords appear to form the outline of a
flat, much-indented vesicle ; however, by more careful observation one
becomes convinced that its contour is often interrupted at the inner
angles of the folds.t The granules of the egg have become grouped in
planes which intersect each other in a line perpendicular to the middle
point of the equatorial plane. Little of this arrangement is to be seen
on the fresh egg, but it becomes prominent on those treated with acetic
acid. When the cleavage begins the cords have increased in number
and have become so arranged that part are directed toward one pole,
the rest toward the other pole. Finally, the egg is fully constricted,
and the cords pass into the daughter cells. The rows of granules stretch
out and may be followed from one cell into the other. Biitschli does
not hesitate, after examining the figures, to identify the “cords” with
the “Kernplatte” and its lateral halves. According to him the inter-
zonal fibres are also indicated in the figure. The same method of
nuclear increase was observed by Schneider in the case of germ-cells of
spermatozoa and numerous other cells of Mesostomum, as well as in the
egos of Distomum cygnoides. tf
* P. S.— The words enclosed in brackets I have interpolated since consulting
the original paper.
+ This description recalls in a vivid manner the figures which Flemming has quite
recently given of the nuclear metamorphosis of tisswe cells in the case of the sala-
mander.
¢ P. S. —Since writing the above, Schneider’s paper (’73, pp. 113 - 118, Taf. V.
Figs. 4. b, 5-8, 11) has been secured. Besides assenting to what Biitschli says respect-
ing the identity of the ‘‘cords” and the lateral halves of the Kernplatte, there are
one or two points to which I would call attention. The interzonal filaments are rep-
resented in Schneider’s Fig. 5. e (Taf. V.) as having each three thickenings, which col-
lectively form, in optical section, three parallel bands of thickenings lying between
MUSEUM OF COMPARATIVE ZOOLOGY. 279
From this it appears probable that Schneider observed the metamor-
-phosis of the nucleus quite as accurately as either of the three remain-
ing observers, but failed to discover that the radiation in the protoplasm
was from two separate centres rather than from a continuous line.*
Fou has observed (’73, pp. 474-476, Taf. XXIV. Figs. 2, 11) that in
the fresh-laid, fecundated eggs of Geryonia the nucleus is unlike the ger-
minative vesicle of the unfecundated eggs. It appears like a vacuole on
account of the refractive power of its substance being less than that of
the surrounding protoplasm. It is possible to distinguish a membrane
(eigene Wandungen) around this vacuole only after treatment with
acetic acid, and then with little distinctness. From this, and its size,
Fol concludes it cannot be identified with the germinative vesicle of the
unfecundated egg, which contains a vesicular germinative dot, but he re-
tains for it, nevertheless, the designation of ‘‘ germinative vesicle.” Just
before the first segmentation this germinative vesicle [primary cleavage
nucleus], has a more confused look and undergoes many changes of form.
the much more conspicuous groups of ‘‘ cords.” The middle one of these three bands
falls in the plane of cell division, and apparently corresponds to the cell plate of
Strasburger.
The figures presented by Schneider recall even more forcibly than the text the
similarity already alluded to, which exists between his observations and those of
Flemming on certain tissue cells. Another point is the discovery, in the formation
of spermatozoa, of cells ‘‘in der Viertheilung” (p. 117 and Fig. 8. 2), presenting con-
ditions parallel to those pointed out by Russow and Strasburger for pollen cells.
The opinion expressed above, that Schneider failed to recognize the radial struc-
ture as centring in two points, is possibly not quite just, for he says (p. 114, 7. ¢.):
“Die polare Anordnung der Kornchen findet man bekanntlich auch beim Furchungs-
process der Ascidien und Seeigel.” Schneider (/. c., p. 188) calls attention in the
explanations of figures to the fact that the polar arrangement of the granules is insuf-
ficiently brought out in Fig. 5. 6. Finally, this metamorphosis, which most likely
occurs in those cases where the nucleus appears to vanish, is not the only method of
cell division. Two methods must be recognized: one in which the nucleus under-
goes the indicated metamorphosis ; the other in which the nucleus retains its form
(p. 115).
* P. S.— Compare this description with the pinnate arrangement of the astral
figures recently described by Fol (’79, p. 167) for Toxopneustes.
Fol seems to have remained for some time ignorant of the discoveries of Schneider,
as he makes, I believe, no mention of the latter’s work except in the paper last cited,
and there (/. ¢., p. 207) states that he knows of Schneider’s work only through
Biitschli’s citation. Since Fol appears to be in doubt as to whether Schneider's paper
was published in the same year as his own paper on Geryonia, or the year following,
it seems to be but a matter of justice to emphasize the fact that Schneider’s paper was
published in April, 1873, therefore about seven months before the paper in which Fol
recorded his observations in the case of Geryonia.
280 BULLETIN OF THE
It soon disappears entirely, but immediate treatment with acetic acid
brings again to view what remains of it, — only a trace (Andeutung) of
the former nucleus, —and at the same time two accumulations of pro-
toplasm, whose closely massed granules assume the form of two regular
stellate figures, one on either side of the remnant of the vesicle. The
rays of these stars are formed by the granules, which are arranged in
straight lines. Many such lines stretch from one star-centre to the
other in an arch, thus embracing the remnant of the “ germinative vesi-
cle.” <A little later the acid fails to disclose a trace of the nucleus, but
the stellate figures are unchanged save that they are farther apart.*
By the segmentation of the yolk these centres of attraction become more
and more separated, and there now appear in each of them one, two,
three, up to eight or ten small vacuoles, which ultimately melt together
and become so rounded as to present exactly the same appearance as the
undivided “ germinative vesicle.”
Such is the formation of the new nuclei. These, with similar obser-
vations on mollusks, worms, etc., lead Fol (p. 487) “to accept in full
Sachs’s theory of segmentation by Anziehungs-Mittelpuncte.” ‘At seg-
mentation the ‘germinative vesicle’ every time disappears, and in its
place there arise in the protoplasm two centres of attraction, in which
latter the new nuclei appear” (p. 486).
Butscutr’s (73%, pp. 101-104, Taf. XXVI. Figs. 61°, 61%) studies
were made on the egg of Rhabditis dolichura, Schneider, without the
use of reagents. They really cover earlier stages in the ontogeny than
the observations of Fol, inasmuch as Biitschli observed the approach and
contact of the two structures which we now know to be the pronuclei.
When the latter have reached the centre of the egg, they appear almost
as though melted together, and the yolk granules become suddenly
grouped radially to the body thus formed. ‘The latter lengthens in the
direction of the long axis of the egg, and assumes a lemon shape. After
some time one observes at either pole of this figure a knoblike protuber-
* When Auerbach (74, p- 254) intimates that Fol’s account is not quite clear,
one has no opportunity to object ; but when he makes Fol responsible for the [im-
plied ?] statement that the nuclei of the first segmentation spheres are produced by a
division of the germinative vesicle, and that the radial figures appear for the first time
in the stages preparatory to the second segmentation, then it must be objected that
the less plausible of two explanations is the one put forward. At least, I see no
reason why Fol may not have called attention to a figure (Fig. 2) representing a cor-
responding stage in a later segmentation (just as Auerbach himself, p. 225, has done)
to illustrate the phenomena of the first segmentation, without involving himself in
the inconsistency with which he has been charged.
MUSEUM OF COMPARATIVE ZOOLOGY. 281
ance, which increases in size, and about which a stellate circle is formed
in the yolk. The knobs continue to separate, while the connecting por-
tion becomes reduced in thickness to a mere thread. This thread of
connection remains some time, but finally during segmentation its halves
are slowly contracted toward the nuclei to form, close to them, a new
knoblike swelling. The radiate figures in the yolk now become less
distinct ; the outlines of the nuclei more definite. During the whole
process of division the contour is confused, and, in addition to the radial
figures of the yolk at the poles of the lemon-shaped nucleus, Biitschli
seemed to see raylike processes stretch out from the nucleus into the
substance of the yolk, which served to strengthen his conviction that the
nucleus possesses at times a considerable degree of mobility. Whether,
however, this phenomenon has anything to do with the radial arrange-
ment of the yolk granules, he did not venture to decide.
The failure to see arched rays joining the two centres of attraction
may readily be understood when it is remembered that his studies were
made exclusively on living eggs.
The subsequent segmentations presented essentially the same phe-
nomena. There is no such thing in his opinion as a disappearance of
the nucleus, although before the division it becomes quite indistinct, a
fact which he is inclined to connect with its mobility.
The conclusion seems to me unavoidable that the knoblike swellings at
the poles of the lemon-shaped nucleus correspond to the centres of the stel-
late figures which Fol saw, and are by Biitschli connected too intimately
(as parts of the lemon-shaped figure) with the nucleus. The knoblike
swellings which are formed at the close of the segmentation out of the
contracting thread are really the new nuclei, for which the centres of
the stellate figures were mistaken. The radiate structure was also ob-
served (p. 35) by Biitschli in the formation of the sperm cells.
In the study of a much less favorable object, Anodonta, FLEMMING (’74,
pp. 286-290, Taf. XVI. Figs. 22-29) was also fortunate enough to see
some of the phases already noticed by Fol and Biitschli. He found that
many of the segmentation spheres under gentle pressure presented near
their centres one or two clear spots without granules, and stretching out
from these toward the periphery in an almost strictly radial direction
rays of clear protoplasm (kérnerloser Substanz), so that the granules
which lay between these rays were likewise arranged in diverging lines.
Subsequent to this condition followed a stage in which two nuclei were
found in the undivided cleavage spheres. In no case were radial struc-
ture and nucleus found to be present at the same time.
282 BULLETIN OF THE
Flemming erroneously concluded that the centres of the peculiar radial
arrangements of the cell protoplasm were probably to be considered as
formative centres (Bildungscentren) for the new nuclei, and asserts that
the segmentation cells of the Anodonta germ actually pass through
stages in which they are without nuclez.*
While Fol and Biitschli agree in the interpretation of the radiate phe-
nomenon as being the result of an attractwe force, they are diametrically
opposed on the old and cardinal question of the persistence or disappear-
ance of the nucleus. While Schneider and Biitschli are in agreement on
this point, Flemming’s testimony is all in favor of the non-persistence of
the nucleus. The last-mentioned observer justly makes prominent the
fact, that the arrangement of the yolk granules is dependent on the con-
dition of the clear protoplasm, — the star proper.
Since the appearance of these four papers much attention has been
given to the phenomena which they discuss.
Whitman ('78%, p. 16) cites Merscunixorr (74) as having seen and
described the radiate structure in Geryonia (p. 19) and Polyxenia. As
regards the entoderm cells of Geryonia (Taf. II. Fig. 7. B), I doubt if
the structure has anything to do with the molecular asters developed
at the time of segmentation. Metschnikoff himself speaks of these irreg-
ular fleecy-looking stretches of protoplasm as the “die bekannten Pro-
toplasmaauslaufer,” which would hardly be the expression to be used
of molecular asters. It is in reality a permanent phenomenon, (if one
may speak of anything as permanent in a growing organism,) which is
most prominent in the least active period of the individual cell’s exist-
ence. In the segmentation spheres of Polyxenia before the differentia-
tion of ectoderm and entoderm (Taf. III. Fig. 3), it may reasonably be
claimed that the rays figured are due to the same influence as those
which induce the molecular stars; but the figure, after all, is hardly more
suggestive of the real aster with its multitudinous rays than are Grube’s
drawings in the case of Clepsine. I do not find that Metschnikoff makes
any explanation of this figure in the text.
* The radical tone of this statement is considerably modified by the very re-
strictive definition which the author formulates for ‘‘ nucleus.” ‘‘ Der Name Kern
kniipft sich fiir uns einstweilen an bestimmte Merkmale : eine Membran oder eine
scharfe Absetzung nach Aussen, einen von der Umgebung verschiedenen Inhalt und
meistens einen Kernkorper.’”’ ‘Die Substanz des nicht mehr sichtbaren Nucleus
wird jedenfalls in irgend einer Form in den Zellen noch vorhanden, vielleicht sogar
localisirt sein ; aber wer sie in diesem Zustand Kern nennen wollte, der wiirde mit
gleichem Recht die Auflésung eines Kochsalzkrystalles als einen Krystall bezeichnen
konnen.” (!)
MUSEUM OF COMPARATIVE ZOOLOGY. 283
SALENSKY (’74%, p. 332) mentions the presence of “ein kugelférmiges
Kliimpchen, welches aus den feinsten Kornchen bestand” within the
germ cell of Amphilina eggs, and is inclined, on the strength of Schnei-
der’s ("73) discovery, to consider it as the altered germinative vesicle.
ScHEnK ('74, pp. 294-297, Fig. 8) describes the appearance of a clear
portion in the middle of the yolk of Serpula, — after the ege has exhib-
ited contractile phenomena and has eliminated the germinative dot, —
which neither occupies the position nor possesses the definite contour of
the vanished germinative vesicle. On the contrary, in a radial direction
it loses itself in the surrounding protoplasm. This nucleus is not an
isolated structure, nor does it differ essentially from the nature of the
yolk, save that the yolk granules are there less abundant. Its increase
accompanies the gradual disappearance of the space at one time existing
between the yolk and its membrane. Sometimes this first nucleus with
its radial streaks appears divided into two parts; this, however, usually
occurs only just before the first segmentation.
Similar stellate nuclei were also seen in vertebrates’ eggs. After
segmentation it is often seen that one of the resultant spheres con-
tains the whole nucleus, while the other only subsequently acquires
one, which is formed just as was the nucleus of the first segmenta-
tion sphere. Schenk concludes by saying that one sees from this that
the nucleus is produced by “a want of uniformity in the distribution
of the granular mass,” and that the nucleus is to be considered as a
central part of the protoplasm, from which it is derived and with which
it is intimately united. Subsequently Schenk (’76, Figs. 2 and 4) saw
stellate figures in the eggs of Echinus after fecundation, and when the
embryo consisted of four segmentation spheres.
The careful studies of AvrerBacH (74, pp. 217-262) on the eggs of
Ascaris nigrovenosa and Strongylus auricularis were especially trust-
worthy on account of their being continuous observations on living egys,
in which, however, a compressorium was employed.
After the complete union, near the centre of the egg, of two nuclear
structures, which we now know to be like those seen by Biitschli, — the
pronuclei, — Auerbach’s observations are to the effect that the resultant
structure becomes elongated in the direction of the long axis of the egg,
and also suffers a reduction of volume. This continues till the structure
becomes a very narrow stripe with parallel edges and pointed ends ; then
it looks like an exceedingly thin fissure in the protoplasm, and finally
disappears ; yet not absolutely without trace, for during this change the
protoplasm surrounding it has become free from granules. This clear
284 BULLETIN OF THE
portion of protoplasm has the form of a dumb-bell, the rodlike middle
portion being the part which contains the “fissure” before its disappear-
ance. From each of the spheres of the dumb-bell stretch out on all
sides rays of clear protoplasm, between which rows or wedge-shaped
masses of granular yolk are embraced. The rays are usually straight,
sometimes slightly bent with the concavity directed toward the centre
of the egg, and give the figure the appearance of two pale suns united
by a long middle piece. The lengthening of the figure continues till the
middle piece is more than half the length of the egg.
The formation of the dumb-bell figure begins with the radial arrange-
ment of the yolk granules about the tips of the broadly spindle-shaped
nucleus, i. e. only when the latter begins to lengthen. The pale rays
intervening between the rows of granules become more conspicuous, and
their bases unite to form the head of the dumb-bell, while the “middle
piece ” is forming.
These phenomena Auerbach explains as follows. The nucleus per-
ishes, and during the lengthening of the nuclear cavity the sap which
fills it penetrates between the molecules of the neighboring protoplasm,
forcing the yolk granules out of it. The rays about the tips of the nu-
cleus are the (physical) expression of the courses along which the fine
streams of nuclear sap penetrate the protoplasm. The distribution takes
place from these tips for two reasons: because the tip of the nuclear
cavity presents a greater amount of surface, as compared with the con-
tents, than any other portion, — hence the point of least resistance ; and
because the sap, on account of the lengthening of the nucleus, is in
motion toward these two points. Subsequently, the resistance of the
lateral walls of the nuclear cavity is so far overcome as to cause the re-
cession of the granules from a thin layer of the adjacent yolk substance.
The nucleus, however, is not the active element. The protoplasm acts
on the passive nuclear sap by changing the form of the nuclear cavity,
and by imbibing the sap. In place of a nucleus there is now in the
yolk a peculiarly shaped territory free from granules, in which all the
substance of the nucleus is dissolved, — the karyolytic figure.
The formation of this figure is followed by the segmentation of the
yolk. The latter is accomplished by a furrow, which, advancing from
one side only, passes through the yolk, or possibly sometimes by an
annular constriction. Soon after the beginning of the segmentation
there appears a vacuole at each of two corresponding points in the stem
of the karyolytic figure near the cleavage plane. These are at first
small, being irregularly and indistinctly outlined. They increase and
MUSEUM OF COMPARATIVE ZOOLOGY. 285
gain circular outlines while they migrate toward the poles of the figure.
They are the new nuclei. They reach or pass the centre of the new
cleavage spheres, but do not reach the swollen end of the karyolytic
figure. The latter meantime gradually disappears. First the stem
becomes slimmer; the rays become shorter, and then disappear; the
centre of the sun becomes flattened to the form of a disk or a meniscus
lens concave toward the cleavage plane; the stem disappears ; the me-
niscus becomes thinner, and also disappears. According to Auerbach,
the new nuclei are formed by the re-collection of the diffused nuclear
sap into a single drop for each sphere ; but inasmuch as each of these
is larger than the half of the old nucleus, additional nuclear sap must
have been extracted from the protoplasm.
It did not fail to impress Auerbach as peculiar that the formation of
the new nuclei should be accompanied by their motion in substantially
the same direction as that which prevails during the dissolution of the
old nucleus, instead of the opposite direction; but it does not seem to
have caused him any misgivings as to the accuracy of his theoretical
propositions.
With Ascaris and Strongylus during segmentation the nuclei never
acquire a membrane, and for this reason the membrane, when it does
exist, must be considered as a secondary structure produced by a conden-
sation of the layer of yolk protoplasm immediately enveloping the nuclear
fluid. The nucleoli arise in the nucleus after it has come to rest, not
before.* In regard to the exact manner of their origin, Auerbach in so
far modifies the opinion held in the first part of his paper as to admit
that they are not necessarily portions of the surrounding protoplasm which
are subsequently detached and set free in the fluid of the nucleus, but
that molecules of protoplasm may have been detached with the formation
of the nuclear fluid, and have remained distributed through it till they at
length became visible by becoming grouped into the observed nucleoli.
The author is also less confident that a multinucleolar condition always
arises by the repeated division of a single original nucleolus.
This method of nuclear increase, to use Auerbach’s own words, “ent-
spricht in der Hauptsache der einerseits von Reichert, andererseits von
den neueren Phytologen aufgestellten Lehre. Aber es ist ausgezeichnet
dadurch, dass die Substanz des aufgeliésten alten Kerns nicht in dem
ganzen Zellenleibe sich tertheilt, sondern in einem beschriinkten inneren,
eigenthiimlich gestalteten, doppelt gegliederten und durch strahlige Fort-
* In the case of the pronuclei, it will be seen that Auerbach says the nucleoli arise
before the former execute their migratory motion.
286 BULLETIN OF THE
siitze erweiterten Bereiche, und zwar unter Verdrangung aller groéberen
Kornchen aus diesem Bereiche.” In his opinion, the old nucleus suffers
complete morphological ruin.
This method of increase of nuclei Auerbach designates as “‘ palingenet-
ische Kernvermehrung,” in opposition to that where no dissolution, but
a direct division, of the nucleus takes place.
The central area of the stellate figures in the case of Limax presents
objections to some of the views which Auerbach entertains. The fluidity
of the nuclear sap should reduce the refractive power of this portion of
the protoplasm ; as a matter of fact the refractive power increases toward
the centre of this area. The stellate centres are often at considerable
distance from the waning nuclear structure, and yet the side of the aster
toward the nucleus shows no differentiation corresponding to the sup-
posed flow of nuclear sap. I have every reason to believe, however,
that in Limax the central area of the stellate figure is, in the words of
Auerbach, “not a nucleus, also not the formative centre of a nucleus,
that it in fact does not even indicate the place at which the new nucleus
appears, and that the latter, even in its migration, does not advance into
[the centre of ] the body of the sun.”
LANKESTER (75, pp. 39, 40) asserts that, in the case of Cephalopods,
the cap of formative matter segregated to the smaller pole of the egg
“presents no nucleus, persistently, though a nucleus may appear in it
at the first.” ‘TI have most fully satisfied myself,” he continues, ‘“ that
temporarily many of the segmentation products are devoid of nucleus.”
The cells which result from the segmentation of the cap of formative
matter Lankester calls ‘“ klastoplasts.” Before the superficial extension
of this cap of klastoplasts has begun, there appear in a deeper stratum
of the yolk pellucid nuclei, at first arranged in a circle around the cap.
These are called “autoplasts.” They are of the same nature as the nu-
clei of cleavage segments. ‘‘I believe in the eggs of Loligo there may be,
according to season, an increase of these nuclei, or, on the other hand,
of these bodies, they being reciprocally vicarious within small limits.”
No area becomes segmented around the autoplasts ; “ they commence as
minute points, gradually increasing in size, like other free-formed nuclei.”
In his preliminary account of the development of Pteropods, Fon
(75, p. 196, also "754, p. 198) says that before each segmentation the nu-
cleus disappears, to be replaced by two molecular stars which arise in its
interior. The centre of each may be considered a centre of attraction :
all the vitelline substance yields to this attraction. After the cleavage
a nucleus reappears at the centre (aw milieu) of each star.
MUSEUM OF COMPARATIVE ZOOLOGY. 287
Burscuut (’75, pp. 210-213) is impelled in his studies on Nematodes
and snails to admit his former notion (that the nucleus simply length-
ens and divides) to be untenable ; but is not willing to follow Auerbach
in concluding that the nuclear substance is distributed through the pro-
toplasm. As regards the nuclei, they are, however, as Auerbach main-
tained, new structures. The most interesting part of Biitschli’s discovery
is the spindle-shaped body (p. 208) an account of which is given in an-
other connection (see p. 536). Of the spindle which occupies the place
of the primary cleavage nucleus after the latter has assumed an unrec-
ognizable state, Biitschli says (pp. 211, 212) it greatly resembles the
spindle just described. In the earliest stages of its visibility there lies
a dark lustrous granule in each fibre at the equator of the body, so that
in a view upon the end of the spindle the granules together form a circle.
Changes, similar to those which occur in the division of the infusorian
“semen-capsule,” now take place. There arise, namely, out of the
simple circle of granules two circles, which move apart toward the ends
of the spindle until they have finally arrived near the middle points of
the future cleavage spheres; then the pointed ends of the spindle are
usually no longer visible, and one sees only the two circles of granules
and the fibres uniting them. Meanwhile the cleavage is nearly com-
pleted. When the formation of the nuclei begins, every distinct trace
of the circles and fibres has disappeared, but what has become of them
he does not know. Reasoning from the first-described spindle and its
supposed origin from the equivalent of the infusiorian “ nucleolus” (the
germinative spot), Biitschli concludes that this spindle must owe its
origin to the nucleolus of the primary cleavage sphere, although he was
unable to recognize this nucleolus at any time previous to the appear-
ance of the spindle. ;
Biitschli also observed that the new nuclei, even in the later genera-
tions, arise, as does the nucleus of the primary cleavage sphere, by the
fusing of numerous nuclei which first grow from minute beginnings to a
considerable size, and which in Cucullanus elegans arise at widely sepa-
rated points. Likewise in Lymneus auricularis there “arise eight or
more small, vesicular, very clear nuclei, containing a number of dark
corpuscles, which are not to be taken for nucleoli.” These nuclei sub-
Sequently grow and successively unite to form a single nucleus,* —
* Oellacher ('72°, pp. 406 - 416, Taf. XXXIII. Figs. 29-36) had already observed
that the nucleus of segmentation spheres in the trout was composed of a cluster (as
many as a dozen) of round or oval bodies varying somewhat in size, and containing
each —at least during the first stages of cleavage —a single nucleolus. Oellacher
288 BULLETIN OF THE :
nucleus of the first segmentation sphere. The formation of the nuclei
in this manner is proof to the author of the untenable position of those
who, like Hiackel, regard such a multinuclear structure as a complex of
cells (p. 213).
Biitschli’s omission of all reference to radial figures about the poles of
the spindle is partly explainable from the transparency of the Cucul-
lanus eggs, which prevents the rays becoming conspicuous, and partly
from the great importance naturally attached to the newly discovered
spindle.
OELLACHER ("74) has described, in a paper which I have not seen, a
radiate structure of the protoplasm as existing just before each act of
Segmentation in the case of the trout. I know only so much of the
substance of this paper as is given by Flemming (’75, p. 207), accord-
ing to whom, the radiate appearance is referred by Oellacher (just as
by Fol and Flemming) to a structural condition of the plasm, not toa
phenomenon of nuclear extinction.
FLemMine (’75, pp. 117-128, 176 e¢ seg. Taf. I.—III.), on the strength
of renewed observations upon Anodonta and Unio together with a ro-
tifer (Lacinularia), in which the entire absence of a nuclear structure
during segmentation is maintained, accepts the views of Auerbach so far
as regards the dissolution of the nucleus (“der morphologische Unter-
gang des Kerns,” p. 117), but presents numerous objections (pp. 188—-
198) to his theory that the radiate structure is due to a distribution of
the nuclear sap from the tips of the nuclear cavity. He is “not yet alto-
gether persuaded of the karyolytic nature of the radial figures” (p. 191).
considered each of these bodies as the equivalent of a cell nucleus, and explained the
existence of a multiple of nuclei in each cell as a precocious activity of the nucleus,
whereby it anticipated by several generations the division which ultimately overtook
the protoplasm. Then with each segmentation half of the cluster fell to the share of
each of the resulting protoplasmic elements. But to explain the continued recur-
rence of a large number of nuclei in each cluster, even after numerous segmentations,
he was compelled to suppose that a process of multiplication was going on among the
nuclei of these clusters, so that they, as it were, kept a definite number of generations
ahead of the protoplasmic spheres to which they belonged, until at length, in the
latest stages of segmentation, this difference becoming obliterated, one could find only
cells with a single nucleus. However, Oellacher remains in doubt as to whether the
multiplication of the nuclei takes place when there are still several in the cluster, or
whether this only occurs when, by successive divisions of the protoplasm and corre-
sponding separations of the components of a cluster, the nuclei have been reduced to
a single one for each cell. No metamorphoses in these ‘‘ nuclear clusters” were seen
by him, and thus the possibility of a confluence of these ‘‘ nuclei” before each seg-
mentation was not, in that case, to be thought of.
MUSEUM OF COMPARATIVE ZOOLOGY. 289
Flemming finds that in Anodonta (Taf. IIT. Fig. 2), after the egg begins
to elongate, previous to constriction, a disklike body, which stains deeply
in carmine, occupies the middle of the clear figure connecting the two
suns, and that a less intensely stained small spherical body occupies the
centre of each sun. The latter he is inclined to think are the begin-
nings of the new nuclei, thus agreeing with Fol as to the place where the
nuclei arise. '
I believe the disklike body is almost unquestionably the nuclear plate,
and not, as Biitschli ("76, p. 248) thinks, the cedd plate.
The two radial figures, which are visible some time before the first
segmentation, and which are of unequal size, (proportionate, namely, to
the size of the two cleavage spheres that are about to be formed,) are no
longer to be seen when the elongation preparatory to cleavage begins.
Flemming is inclined to interpret (p. 128) the existence of single cells
containing, as previously reported by himself, two nuclei, to be a pa-
thological phenomenon, although stating as a possible explanation that
it may not be of so much importance, after all, whether the new nucleus
arises a little sooner (before division), or a little later (after cleavage).
In Lacinularia the only noticeable difference from Anodonta is to be
found (p. 183) in the fact that the centres of the radial systems are not
such distinctly limited clear spots as in the egg of the latter.
The primary (Keim) as well as later segmentation spheres divide while
in the cytode condition (p. 184).
His (75, pp. 35-39) contributes no new observations touching the
question, Whence arise the parablastic cells? although he urges grounds
against considering them derivatives from the cells of the germ layer.
Indirectly, therefore, he implies that they arise de novo in the cortical
layer of the yolk (Rindenschicht) and that their nuclei have not arisen
by a process of division. }
Soon after his last-mentioned paper, Birscuii published (’75*) fur-
ther observations on the nucleus and its metamorphoses during cell
division. The investigation of the contents of the testes in the case of
Blatta resulted in showing that the nuclei of the multinuclear germ cells
of spermatozoa did not undergo such a fusion as he had observed in the
cases Just reviewed, and as he expected. to find here. The phenomena
accompanying the division of the germ cells were, however, a striking
repetition of the changes traced in his previous paper. In one point
only does the author find reason to change his views. He now concludes
that the spindle-shaped body results from the metamorphosis of the
whole nucleus, not simply of the nucleolus. The nucleus suffers a con-
VOL. Vi.— NO. 12. 19
290 BULLETIN OF THE
siderable reduction in size through loss of nuclear fluid (Kernsaft) ; it
also loses its sharply defined membrane, although the existence of a
delicate one around the spindle the author finds probable from analogy
with the infusorian “‘ semen-capsule.” When the halves of the equatorial —
zone have reached the ends of the spindle, the surrounding protoplasm
exhibits the radial structure already seen in other cases. Accompanying
a constriction of the protoplasm the nuclear spindle assumes a bandlike |
appearance, with the dark granules of the zones occupying the ends of
the band near the centre of the nascent cells. The constriction of the
cell protoplasm is completed, and the two cells remain united only by
the band. The formation of the new nuclei now begins by the appear-
ance of a small, inconspicuous, clear space, filled with fluid, around the
dark granular mass of the ends of the band. The dark granules pass
into the interior of the new nuclei, and are the nucleoli. It is probable
that the fibres of the band divide in the middle, and that the halves are
absorbed into the corresponding nuclei. Very nearly identical results
were also obtained in the study of the embryonic red blood-corpuscles
of the common fowl.
The following conclusions are, among others, drawn by Biitschli: that
the nucleus does not disappear in cell division, but only undergoes
a very remarkable reconstruction (Neubildung) ;* that the karyolitic
figure of Auerbach is most decidedly to be considered as the modified
nucleus. A complete dissolution of the nucleus is not to be thought of.
It is evident from this paper that Biitschli now finds himself more at
variance with the conclusions of Auerbach than previously. Although
the author here refrains from expressing his opinion of the signification
of the radial figures, he remarks that to a certain extent he agrees with
Auerbach’s views. Biitschli does not seem to have observed that these
radial figures arise before the complete formation of the spindle, and
does not mention. them as existing till the time when the lateral zones
reach the end of the spindle. His figures published by Strasburger
show, however, that he had observed these stars before the division ot
the median zone.
* Lest ‘‘reconstruction” may appear an unwarrantable rendering of ‘‘ Neubil-
dung,” I take the liberty to quote the context, which will show the author’s real
meaning. I must draw, says Biitschli, the following conclusions: ‘‘Dass der Kern
bei der Theilung thatsiichlich nicht schwindet, sondern nur eine héchst eigenthim-
liche Neubildung erfahrt und dass die vielfach behauptete Neubildung der Kerne der
Tochterzellen nur insofern dem thatsiichlichen entspricht, als dieselbe eine Umwand-
lung des in so eigenthiimlicher Weise modificirten Kernes in eine seiner urspriing-
lichen entsprechende Form ausdriicken soll.” (p. 430.)
MUSEUM OF COMPARATIVE ZOOLOGY. 291
From Fou’s (’75*, pp. 108-112) memoir on the Pteropods one learns
that the nucleus of the fecundated vitellus, or the germinative vesicle (as
he still continues to call the primary cleavage nucleus), arises by the
fusion of two or three corpuscles at the centre of a molecular aster whose
rays disappear during the fusion. This nucleus, which attains some-
times a third the diameter of the whole vitellus, occupies the centre of
the formative protoplasm ; the latter is smaller than the nutritive por-
tion of the vitellus, and the two meet ina plane. Although it shows a
fine stippling, the nucleus is much more homogeneous than the proto-
plasm itself, and also less fluid. The nucleolus is always wanting. A
nuclear membrane can be demonstrated easily after contact with sea-
water or reagents, but this does not warrant the conclusion that it exists
in the living condition.
After an interval of repose the nucleus disappears ; but just before it
ceases to be visible there appear on opposite sides, at the boundary be-
tween it and the protoplasm, two points, which differ but little from it
in refractive power. Straight rays soon diverge from these points into its
interior: they rapidly increase in number, and become elongated until
those from the opposite sides meet in the middle of the nucleus, which
at this moment disappears. No trace of rays is to be seen outside the
nuclear vesicle in the living egg, but acetic acid causes also this portion
of the aster to appear. If applied before the nucleus becomes invisible,
the acid causes it, contrary to the case of Geryonia, to disappear.* The
rays extend to near the periphery. The central part of each star is
easily distinguishable without the use of acid, but is more distinct with
it. The rays occupying the place formerly filled by the nucleus are often
inflected, and pass from one star to the other. Soon after the nucleus
disappears, the stars move apart. After a time a furrow is to be seen on
the surface of the yolk running at right angles to a line joining them.
Acetic acid develops, just before the appearance of the furrow, a very
distinct line [plane ?] of demarcation between the two stars. This line is
formed of granules, which are a little larger than those of the rest of the
protoplasm. As the furrow deepens and surrounds the yolk, it assumes
& position oblique (in a constant direction) to the line joining the asters.
It is during the approach and mutual flattening of the cells that the new
nuclei appear at the centre of the protoplasmic part of each cell. Fol
further states (75%, p. 180) that he has never yet seen segmentation
preceded by a division, properly so called, of the nucleus, but would not
* P. S. — Fol (’79, pp. 219, 220) has since corrected and explained the cause of
this error.
292 BULLETIN OF THE
dare to assert that this mode does not exist among animals. Even in
the case where the nucleus disappears, however, it in all probability
forms none the less the central part of the molecular stars; and as it is
in the centre of these stars that the new nuclei reappear, it may be pre-
sumed that the latter are, at least in part, composed of the very sub-
stance which constituted the nucleus before its division.
It is the origin of the new nuclei at the centre of the asters which is ;
most strikingly in contrast with the results obtained in studying Limax. |
Fol also failed to recognize the fact that the deflected rays, which com-
pose what is now known as the spindle, were in any essential respect
peculiar. This oversight may have had its influence in preventing the
author from giving an accurate account of the method in which the new —
nuclei arise.
The “line” of coarser granules may have been the first trace of the
forming ‘‘ Kernplatte,” although no connection with the bent rays that
pass from pole to pole of the spindle was indicated by the observer.
Compare Fol’s Fig. 5, Plate VIIL., with Fig. 82 of Limax.
In another point there is conmidonalitn divergence between Fol’s ac-
count and my own observations. In Limax the asters can be made vis-
ible by the use of acetic acid much earlier than is represented in the
case of Pteropods. Might they not have been demonstrated by Fol
for a somewhat earlier stage (e. g. for that shown in Fig. 2, Pl. VIL)
by a more careful or prompt employment of acetic acid? If not, then
we have to do in these cases with heterochronic variations. The com-
parison may be taken to afford ontogenetic evidence of a palingenetic con-
centration of the events of nuclear metamorphosis in the case of Limax.
What the immediate motive to such an acceleration may have been, it is
not easy to conjecture.
STRASBURGER (75). The reader is referred to p. 372 for a synopsis
of the results of Strasburger’s studies, as the first edition of his work has
not been accessible.
The first of a series of valuable articles by O. Hertwic (’75) embraces
the results of observations made chiefly on Toxopneustes lividus. The
results obtained by the use of hardening reagents were controlled, as far
as possible, by studies of the living egg. Around the nucleus of the first
segmentation sphere (Furchungskern) the protoplasm has a radial arrange-
ment which stretches to the periphery of the yolk, and in the immediate
vicinity of the nucleus there gradually collects a homogeneous substance
destitute of granules ; furthermore, the nucleus itself undergoes a slight
change of form, which is interpreted as the result of its amoeboid motion.
MUSEUM OF COMPARATIVE ZOOLOGY. 293
Owing to both these changes the contour of the nucleus is less distinct
than in the unfecundated egg. Its changes of form lead after a time to its
permanent elongation. Its two poles are occasionally truncate, so that,
in osmic acid preparations, it has the form of a cask. With this treat-
ment the nucleus is homogeneous. Meanwhile the poles of the nucleus
have become the centres of an accumulation of homogeneous substance,
which forms at first a small area, and then enlarges in all directions.
The formation and enlargement of the areas is accompanied (1.) by an
arrangement of the yolk granules in rays directed toward the nuclear
poles as centres, and (2.) by the growth of the suns thus formed by means
of a peripheral elongation of their rays. The poles of the nucleus be-
come in the living egg indistinct, and finally the nucleus suddenly disap-
pears; but eggs treated with acids teach that the nucleus assumes the
form of a bent spindle, each of whose tips appears as a conspicuous dark
granule in the centre of its area. Later, the thicker middle portion
of the spindle exhibits a number of dark, coagulated, intensely stained
rods (Stibchen), lying parallel to the long axis of the spindle, and ap-
pearing in optical section of the latter as a circular cluster of granules,
which in Hertwig’s figure (Fig. 27. a and d) appear evenly distributed
over the whole area of the circle. From the intense staining it is
concluded that these rods consist of condensed nuclear substance, on
account of which they are collectively named the middle zone of thick-
enings (mittlere Verdichtungszone). This structure is referable to a
process of differentiation in the nucleus similar to that which takes place
in the formation of nucleoli (p. 414).
After the apparent dissolution of the nucleus, the two suns are con-
nected by a narrow non-granular band, which occupies its place (dumb-
bell figure) ; the peripheral ends of the rays extend either to the surface
of the yolk, or to a plane (Theilungsebene) perpendicular to the middle of
the band, and the deep ends approach the centres of the suns with such
want of uniformity as to give the homogeneous area an irregular outline.
The nature of all such “ Radienfiguren” is explained (pp. 415, 416) as
resulting from a force which is exercised by the nucleus and expresses
itself in an attraction of the homogeneous protoplasm, so that the radial
arrangement of the yolk granules is only the optical expression of the
disposition of the protoplasm in which they are imbedded. The granules
are replaced by the protoplasm in the vicinity of the nucleus, since the
latter exercises no attractive influence upon them. The attractive force,
at first operating uniformly in all directions about the “Furchungs-
kern,” is distributed at the time of the lengthening of the nucleus to its
294 BULLETIN OF THE
poles, and increases with the increase in the distance between the poles,
attaining its maximum in the dumb-bell stage, after which (at division
of the nuclear band) it wanes and altogether disappears. The elonga-
tion of the nucleus and the radial figures are together comparable to the
magnetic rod and its influence on iron filings, without, however, necessi-
tating the implication of an identity of forces.
About the time the nucleus begins to elongate, the outline of the egg
undergoes for a short time a series of changes in form (pp. 403, 404,
417), consisting of low elevations. In the dumb-bell stage the egg elon-
gates in the direction of the handle of the dumb-bell, and a circular furrow
appears in the plane of division and finally effects the separation of the
halves. This constriction is often accompanied by irregular changes of
the surface in the form of lobed pseudopodial processes, which here and
there arise and disappear. This phenomenon presumably has a causal
relation with attractions in the nucleus.
The further changes, as seen in the interior of the living egg during
and after the constriction of the yolk, begin with a separation of the
-heads of the dumb-bell figure, and a modification of their form. Each
is at first flattened in a plane parallel with the division plane, and then
becomes a meniscus, the concave surfaces of the two meniscuses facing
each other and continuing in connection by a thin pedicel. About the
time the constriction divides the yolk, there suddenly appears a small
clear spot in each half of this pedicel, at some distance from the divis-
ion plane, and this spot, which is at first of irregular form, becomes
rounded and increases in size; it is the nucleus of the daughter cell.
Next, the radial arrangement of the yolk disappears, then the pedicel
vanishes, the nucleus migrates partly into the meniscus, and finally the
latter is reduced to two small areas at the sides of the nucleus. The
newly formed nuclei in this, as well as in all subsequent stages, are with-
out membrane, and consist of a homogeneous substance. Inasmuch as
the nuclei are of nearly uniform size for the first few generations, it fol-
lows that a considerable increase in the nuclear substance has taken
place after each segmentation.
Osmic acid preparations stained in carmine furnish additional infor-
mation on these internal changes. Preparations of eggs somewhat older
than those exhibiting the “middle zone ” show a ribbon-shaped body in
its place. Its ends reach into the middle of the suns, and, owing to the
intensified action of the reagents, appear as dark sharply defined streaks.
Where the band enters the head of the dumb-bell it presents rodlike
thickenings (seitliche Verdichtungszone des Kernbandes).
MUSEUM OF COMPARATIVE ZOOLOGY. 295
Between these zones lies the ‘‘ middle piece” ; beyond them the “end
pieces.” Each of these is homogeneous, slightly reddened, and only
rarely striate in osmic preparations; but in chromic acid preparations
fine streaks are seen to connect the rods of one lateral zone with those
of the others. During the constriction of the yolk, the nuclear band
lengthens, the two lateral zones continue to move apart, and lose their
striate differentiation. In place of the rods are larger or smaller gran-
ules, and drops which have arisen by a confluence of granules, or it may
be a single dark red mass with a knobbed surface. The end of the
band is broadened, and its corners are drawn out into two prolongations
(Spitze), which appear as dark granules. After the completion of the
constriction, the lateral zones gradually become thicker and finally as-
sume the spherical form, and the middle and end pieces become shorter
and disappear by uniting with the rest of the nuclear mass. Thus the
nuclei of the daughter cells arise in the parts of the nuclear band called
lateral zones. ; .
These phenomena may in their interpretation be divided into two
groups, says Hertwig; the one relating to the changes of the nucleus,
the other to those of the yolk. They accompany each other in such a
manner that each form of the nucleus corresponds to a definite method
of arrangement of the protoplasm, so that an intimate connection between
the two must be inferred.
In considering whether the impulse to division proceeds from nucleus
or protoplasm, Hertwig says that it is from the former, and “therefore
considers the nucleus as an automatic centre in the cell equipped with
active forces.” The lengthening of the nucleus is to be considered, like
its earlier amoeboid changes, as the result of active phenomena of motion
on the part of the nucleus, yet with this distinction, that the displace-
ment of particles is now only in two directions, instead of in all direc-
tions. The two poles of the nucleus exert a repulsive influence upon
each other, and determine the distribution of the remaining nuclear
mass. ‘The two lateral zones arise out of the middle zone,* and migrate
* A statement made by Priestley ("76, p. 152) in his review does not seem to reflect
in a very accurate manner the ideas of Hertwig as to the connection between the mid-
dle zone and the nuclei of the newly formed cells. The sentence in question is as
follows : —
** Although Hertwig in his hardened and stained specimens does not certainly
speak of the derivation of the young nuclei from the first median thickened zones [zone],
there can hardly be a doubt that the lateral thickened zone{s] (which afterwards be-
came the nuclei) correspond entirely to the segments of the nuclear disk described by
Biitschli, Strasburger, and Beneden, and resulted from division of the former zone.” If,
296 BULLETIN OF THE
toward the ends of the nucleus without fully reaching them. As the
rods (Stabchen) of the middle zone arise by a differential process which
separates ‘nuclear substance” from ‘nuclear sap,” so the new nuclei
arise by the reverse process, — the rods imbibe nuclear sap, swell, and
form granules which melt together to constitute the nuclear mass. A con-
densation of nuclear substance is likewise the cause of the dark granule
at the end of the spindle and the dark streak at the end of the nuclear
band. The “ Radienfiguren” consist in a radial grouping of the proto-
plasm around the nucleus or definite points of the same.
It is concluded, further, that ‘the division of the nucleus is a process
entirely independent of the division of the protoplasm,” since in certain
egos, which probably had gradually succumbed to the effect of external
noxious influences, the division of the nucleus was not followed by a cor-
responding process on the part of the protoplasm.
The two main results which Hertwig deduces from the foregoing are : +
(1.) In egg segmentation a dissolution of the nucleus does not take place ;
the nuclei of the segmentation spheres are rather parts (Theilstiicke) of
the maternal nucleus. The supposed disappearance of the nucleus be-
fore division is explainable from its peculiar changes of form, by reason
of which it becomes less easily recognizable in the living object. (2.) In
cell life a high physiological significance belongs to the nucleus, for it
must be considered as an automatic force-centre. In cell multiplication
this especially comes into activity, inasmuch as it impels and regulates
the same.
For the most part I can only confirm the views entertained by Hert-
wig; in one or two points, however, I find a difficulty in adopting his
opinions. The amceboid changes of form which the nucleus presents are
probably referable to an inherent activity of the nucleus, which warrants
the conclusion that it is an automatic centre in the cell; it seems less
certain that the elongation of the nucleus and the appearance of two
centres of attraction are referable to the same force resident in the nu-
cleus. In the first place, only two substances are recognized as entering
into its composition, —a nuclear sap and a nuclear “substance.” The
latter is the active component. If, as Hertwig seems to infer, that part
as seems to be the case, Priestley entertained the opinion that Hertwig had failed
to draw and to formally express a conclusion establishing a genetic connection between
the new nuclei and the median zone, then it is probable that the following passage
must have been overlooked by him: ‘‘ Aus der Aufeinanderfolge der verschiedenen
Bilder glaube ich den Schluss ziehen zu diirfen, dass die beiden seitlichen Verdich-
tungszonen aus der mittleren entstanden sind.”’ (Hertwig, p. 414.)
MUSEUM OF COMPARATIVE ZOOLOGY. 297
of the nuclear “ substance’ which is accumulated at the poles of the elon-
gated nucleus exerts an attractive influence on the surrounding proto-
plasm, it seems only natural to inquire why the greater mass, accumulated
at the equator, does not exercise a like influence, and why it is that the
latter seems to respond quite as passively as the protoplasm to the at-
tractive influence of the centres of the asters. I am inclined to think
that the astral phenomena are not to be explained so simply as by the
assumption that they are due to the attractive influence of a segregated
portion of the nuclear “substance” as such ; but that it is more likely
they arise in response to a force set free by rapid chemical changes at
definite points in the protoplasm. From the usual proximity of those
points to the nuclear structure, it seems highly probable that the chemi-
_ cal changes are sustained by the direct mingling of the substance of the
nucleus with the protoplasm; there are some cases, however, (e. g.
Limax,) where the evidence of a direct mingling is wanting, — where
the early participation of the substance of the nucleus may possibly be
called in question.
Hertwig maintains the morphological integrity of the nucleus through-
out the metamorphosis. If such is the case, are we not justified in ex-
pecting that its attractive influence will continue to be exerted from the
beginning to the end of the process? In that event, the two asters
which arise with the lengthening and polar differentiation of the nucleus
ought to be genetically connected with the sengle aster which first radi-
ates from the “ Furchungskern.” Selenka, it is true, has recently main-
tained this very position, but I believe that Hertwig (p. 416) is right
when he practically denies the existence of a genetic connection in saying :
“Dann lost sich die alte Radienfigur allmiilig auf und es entstehen zwei
neue an den beiden Polen des Kerns. Dieselben sind anfangs klein,
u. 8s. w.” Hertwig believes the amphiaster becomes explainable as the
result of the attractive influence of the nucleus on the protoplasm, as
soon as we assume that with the lengthening of the nucleus there is a
distribution of the forces of attraction to its poles.* I find nothing to
support this conclusion, since I see no evidence of a genetic connection
between the single and the double asters. Both may be the result of
like chemical changes, but certainly the latter are not referable to the
_ direct attraction of the nucleus, or a segregated portion of it.
* “Auch diese Erscheinungen erklaren sich aus einer Anziehung, welche der Kern
auf das Protoplasma ausiibt, wenn wir annehmen, dass die zu Anfang in der Kern-
kugel nach allen Richtungen gleichmiassig wirkenden Anziehungskrifte bei der
Streckung des Kerns auf die zwei Pole desselben sich vertheilen.”
298 BULLETIN OF THE
I am not prepared, then, to grant that the “ Anstoss” to the processes
of cell division proceeds from the nucleus; nor does it seem to me im-
peratively necessary to accept the other horn of the dilemma offered by
Hertwig. From purely a priorz considerations, one might be inclined to
think the initiative lay with the protoplasm, for in that event the divis-
ion of a cytode would not demand a special explanation different from
that of cel division ; but with the view I have suggested it is perhaps as
inappropriate to inquire which takes the initiative as it would be to ask
whether the carbon or the oxygen begins the process which results in the
production of heat.
There is ground for believing that in Limax the whole of the “ middle
piece” does not enter into the composition of the new nuclei, but that
portions of the interzonal fibres remain permanently near the surface of
the vitellus. 1
The flattened or band-like condition of the spindle I have not seen ;
it is probably of rather limited occurrence. I have not been able to dis-
cover Hertwig’s so-called end-pieces, or, to be more exact, I have not
seen the nuclear fibres reach the centre of the sun. This, after all,
varies with the particular stage of advancement, for practically the rays
and spindle fibres in the beginning reach almost to the centre of the
aster. It is in the later stages (when, for example, a confluence in the
elements of the lateral zones has begun) that I fail to find evidence of
the continuation of the fibres beyond the region of the lateral thicken-
ings.
In his preliminary note on the development of Heteropods, Fou (75°,
p. 472) says: ‘Here also the nuclei disappear before each segmentation,
and are replaced by molecular stars.”
In his history of the development of Bombinator igneus, GorTTE (’75)
describes the events which succeed the fecundation of the egg substan-
tially as follows.
After the disintegration of the germinative vesicle there ‘arises, prob-
ably near the centre of the yolk, a ‘“vitelline nucleus” (Dotterkern)
which is not histologically distinguishable from the surrounding yolk.
Between this nucleus and the finely granular substance left behind by the
germinative vesicle there is only a chance [i. e. no genetic] relationship
(p. 51). Owing to the absence of coarser yolk corpuscles (Dotterplattchen) _
from this nucleus, and to the dark color of the finely granular substance
which takes their place, the outline of the nucleus is visible. It migrates
toward the surface of the yolk, whereupon there arises within it a deli-
cate round corpuscle, — the first “life-germ” (Lebenskeim). The vitel-
MUSEUM OF COMPARATIVE ZOOLOGY. 299
line nucleus is, in Goette’s opinion, certainly the initiatory point of the
whole development. Subsequently its outline melts away, and with it
the significance of the nucleus itself; the “life-germ,” however, remains,
and surrounding it — though not sharply marked off from it — an area
of fine-granular yolk substance, which is not constant in size, nor in the
sharpness of its limitation from the remaining yolk (pp. 54, 55).
Soon after its formation the life-germ is elongated in a direction
transverse to the axis of the egg. Its ends enlarge at the expense of
the middle portion, which continues to grow more slender as the ends
diverge from each other. It at length breaks, and the halves become
rounded, having meantime begun to increase, so that eventually each
attains the size of the first “‘life-germ.” As observed in subsequent life-
germs, the elongation results from a change in the form of the germ,
whose remaining axes shorten, and is not, therefore, due simply to a
growth at two opposite points (pp. 55, 60). From what is said of the
division of the jirst life-germ (p. 55), one would infer that the changes of
the surrounding “area” followed those of the germ ; but it is distinctly
stated in another place (p. 61) that this finely granular substance of the
area initiates the motion in two opposite directions, itself dividing into
two masses before the germ does.
After the second division of the yolk, there is an essential change in
the contents of each life-germ; namely, a variable number of round,
clear corpuscles appear in the apparently homogeneous germ-substance,
which are the “nuclear germs” (Kernkeime). These are so soft that
they become elongate at the subsequent division of the life-germ.
While the Kernkeime augment and thereby consume the substance of
the latter, it, together with its surrounding “ area,” melts into a single
delicately granular mass, in the middle of which the compacted Kern-
keime fill up the space which the original life-germ had occupied.
As the nuclear germs supersede the fe-germ spatially, so they do
functionally in the subsequent divisions of the yolk. During the mul-
berry stage the division occurs so rapidly that the nuclear germs have
not time to attain the centre of the finely granular mass before the lat-
ter has begun to elongate preparatory to the next division, which is
usually effected along a plane perpendicular to that of the last preced-
ing. At the close of the division the fine-granular mass appears radi-
ally streaked about the nuclear germ [aster], and likewise delicate dark
lines converge from the plane of division toward each of the germ masses
[spindle]. New nuclear germs constantly arise, not so much by division
as probably out of the amorphous fine-granular mass, and associate
themselves with those already formed.
300 BULLETIN OF THE
Such, according to this author, is the nature of the process for only
a limited number of segmentations, however. Toward the end of yolk
cleavage — when the segmentation begins to be no longer easily dis-
cerned by the unaided eye — the cluster of nuclear germs (Kernkeim-
haufen) melts together into a solid corpuscle, which retains for some
time an irregular outline and anetlike pattern, — the last trace of its
composition out of separate nuclear germs, but which eventually becomes
a sharply defined, round, finely granular “ cell nucleus.” The division
of the cell nucleus results from a one-sided outgrowth, not from an elon-
gation, as in earlier segmentations.
It is impossible to review here in detail the extended reasoning put
forward by Goette to show that neither the unfertilized nor the fecun-
dated egg are living substance, and how that, during the yolk division,
both the whole yolk sphere and the individual yolk masses [segmenta-
tion spheres] are lifeless stages of transition from unorganized matter to
an actual [living] organism (p. 77).
Having discovered that the physico-morphological conception of the
cell is incompetent to stand for a complete definition, he seems to fall
into an equally exclusive method of reflection, and denies that the egg
is a cell because it fails to exhibit to him one of the functional peculiar-
ities of living things. It does not live because he discovers no process
of nutrition (Ernihrung), and that there is no such thing as a nutritive —
function is confirmed, sufficiently for him, by the single fact that the
egg does not grow, — does not increase in size, except in a manner quite
foreign to the method of growth in living cells. Thus denying the ad-
equacy of the morphological conception, he will not even allow any other
functional manifestation than that of growth to stand in evidence for the
living condition of the egg, or its real cell nature. The motive to such
a theory of the transition of lifeless to living matter has, to say the
least, not been strengthened by the accumulating evidence of a genetic
connection between the germinative vesicle aud the subsequent genera-
tions of nuclei.
According to Goette, the formation of the “life-germ” and its area
is only the result of a radial diffusion (p. 88), the optical expression of
which has already been noted, and the life-germ, in its turn, causes in a
certain way the continuation of this diffusion.. The only essential dif-
ference between the developing and the not-developing egg lies in the
regulation in one case, and the want of regulation in the other case, of
the osmotic process which takes place in both instances between the
yolk and the water surrounding it.
?
MUSEUM OF COMPARATIVE ZOOLOGY. 301
There is one point in Goette’s account which seems to me cor-
roborative of the views I hold about the nature of the asters. The
fine-granular area surrounding the nuclear germ elongates before the
latter undergoes any change of form. Whitman (78%) has observed a
similar instance in the case of Clepsine, but has interpreted the elon-
gating area as a nucleus. I believe that Goette’s nuclear germ and
Whitman’s nucleolt are the same, and are really nuclez, and consequently
that the “granular area” of the one and the “nucleus” of the other
are both cell protoplasm, so that in these two cases the first optical evi-
dence of a coming division is manifested, not in the nucleus, but in the
protoplasm immediately surrounding it.
Very little attention is bestowed by Kowatevsry (’75, pp. 609, 610)
on the changes in the nucleus and cell protoplasm during segmentation,
as observed in Pyrosoma. The first division of the formative yolk is
effected by a furrow, which, beginning on one side, sinks deeper and
deeper, and near which is observed in each segmentation ball a nucleus
of stellate form (Fig. 13). An examination of the figure is sufficient to
convince one that the author has overlooked the real nucleus, and has
taken therefor the stellate figures in the protoplasm of the cell. The
reader will recall the fact that Kowalevsky had previously (71) main-
tained that the stellate structure was limited to the nucleus, and will not
be surprised to find that this opinion has caused him to portray these
figures with an abruptness of outline (Fig. 14) which is not often seen.
The rays in the figure alluded to are even made to terminate distally in
slight enlargements.* Nothing in the figure would indicate that this
observer saw anything of the spindle-shaped condition of the nucleus, or
of the nuclear plates, which is the more surprising, if staining was re-
sorted to for these earlier stages, as it certainly was for later ones.f
The author thinks it probable that a division of the nucleus precedes
that of the yolk, although he has not directly observed it.
* Although Eimer (’77, Figs. 13, 18, etc.) has recently shown that similar nuclei
are found in tissue cells, and especially in Coelenterates, I am still inclined to think
that Kowalevsky’s ‘‘nuclei” are stellar arrangements of the cell protoplasm, such
as exist in the case of many other animals.
1 If I am wrong in considering these radiate lines as belonging to the protoplasm
rather than to the nucleus, then they probably can only be considered as the spindle
fibres of a nuclear spindle seen endwise, much as depicted by Strasburger ("76, Taf.
Vil. Fig. 18 a). There is, however, a serious objection to this explanation, for two of
the cells in Fig. 14 (Kowalevsky) are in an advanced stage of segmentation, and are
30 located, with respect to the observer, that the spindle could have been seen only
nv face, — not end-wise !
302 BULLETIN OF THE
In a stage somewhat later than the mulberry stadium, a section of
the embryonic cell-mass — which is grouped about one pole of the egg —
shows (Fig. 17) in each cell a nucleus (about which the protoplasm in
the figure is shown to have a faintly radiate arrangement), with one or
two nucleoli, and numerous cells in process of division (p. 610). Be-
tween the cells of uniform appearance there are found a few which
differ from them in being smaller, more intensely stained, and in pos-
sessing very little protoplasm about the nucleus. Whether these latter
are identical with the ‘“ cells in process of division,” the author does not
state.
Notwithstanding the admitted insufficiency of his observations on the
development of the eggs of the rabbit, Ep. van BENEDEN ('75, pp.
704, 705) believes he may affirm that the supposed [nuclear] vacuoles,
which, according to Auerbach, appear in the karyolytic figure during
the first segmentation, are not newly formed elements, but fragments of
the first embryonic nucleus, which has changed from a spherical to a
fusiform condition. They (vacuoles) are bodies formed from nuclear
substance; they become rose-colored in picrocarmine. Each sphere,
at the end of the first segmentation, presents a regularly spherical form,
and discloses a clear spot composed of two distinct parts. The smaller
one, derived from the first embryonic nucleus, is called pronucleus dé-
rwvé ; the larger, with a bunched surface, and incompletely enveloping
the smaller one, is named pronucleus engendré. The latter is only the
remnant of the homogeneous, transparent substance accumulated in the
first sphere at the two poles of the first nucleus after the latter has
taken the form of a spindle. It is a differentiated portion of the proto-
plasm of the cell in process of formation, and presents no genetic bond
of connection (lien) with the nucleus of the first sphere. The pronucleus
dérivé grows at its expense, finally absorbing it completely. The “ de-
rived pronucleus” thus becomes the nucleus of its vitelline sphere, and
contains numerous refringent nucleoli.
The spheres, some time after division, lose their spherical form, and
become mutually flattened, in which state the “ pronuclei” have given
place to a single nucleus.
Chapter VI. of this preliminary communication is devoted to cell
multiplication. The réswmé of results from the study of the ectoderm
cells, in the case of the rabbit (pp. 732-736), do not differ very mate-
rially from the results of Biitschli and Strasburger. The first phenomena
which announce the approaching division of a nucleus have their seat
partly in the nucleus itself, and partly in the body of the cell. The
MUSEUM OF COMPARATIVE ZOOLOGY. 303
contour of the former becomes indistinct, and its form irregular, owing,
possibly, to its amoeboid movements. The nucleoli disappear. The
substance of the nucleus is soon divided into two parts: the one, which
is clear and transparent, and which is not colored in either carmine or
hematoxylin, is the suc nucléaire; the other, which is likewise homo-
geneous, but which becomes deeply stained, and forms an irregular
lump (grumeau) in the middle of the nucleus, is the essence nucléacre.
The nuclear sap accumulates at the two poles of the elongated nucleus ;
the “essence,” at the middle of the nucleus, to form the equatorial
plate. The faces of the latter are bunched, and consequently irregular.
It seems formed of very refringent globules of an ovoid, or of a rod-like
form. Whatever the method of treatment, the nucleus was never found
at this time to be striated, either longitudinally or transversely. The
body of the cell undergoes concomitant changes of form ; it also be-
comes more granular, and slightly stained by coloring fluids, these lat-
ter peculiarities serving to distinguish at once the cells in process of
division.
The nucleus becomes spindle-shaped, then flattened (rubané). At its
poles there accumulates, in the body of the ‘cell, a little clear, finely
granular substance, which the author hesitated to identify with his
pronucleus engendré, though he would at present probably not entertain
any doubt as to the correctness of this identification. This polar mass
becomes the centre of a stellate figure developed in the protoplasm of
the cell, and indicates very manifestly the attraction exercised by the
poles of the old nucleus upon the protoplasmic substance of the cell.
These stellate figures, already seen by numerous observers in segmenta-
tion spheres, have not been previously pointed out, so far as the author
knows, in ordinary cells.
The equatorial granular plate divides into two parallel disques nu-
cleaires, which separate as though mutually repulsive. These two plates
are connected by filaments (Kernfiden of Strasburger), which appear
to be thrown out by some of the granules which constitute the disks.
After the disks have separated from each other, these filaments are
drawn in, and blend with their substance. Meanwhile, the nucleus
takes the form of a band with parallel edges, and the nuclear sap (very
faintly rose-colored in picrocarmine), which had at first been repelled
to the poles of the nucleus, is accumulated between the two disks. The
latter finally reach the extremities of the nuclear band, and come into
immediate contact with the small, clear mass at the centre of the stel-
late figures. The clear band, which is the remnant of the old nucleus,
304 BULLETIN OF THE
is now composed of the two disks and a piece intermédiaire, the latter
being only slightly, or not at all, stained. During the constriction of
the body of the cell, which now takes place, and which does not en-
croach upon the band, there occurs in the piéce intermédiaire a differ-
entiation of substance at the niveau of the constriction. Treatment
with nitrate of silver causes the appearance of black points, which
become more and more numerous. These at length become aligned,
and form the partition separating the two produced cells. The parts
of the intermediate piece adjacent to the partition blend more and
more with the cortical zones of the produced cells; the part adjacent
to the polar disk becomes, on the contrary, granular, and gradually
blends with the medullary mass of the cell. The polar disk becomes,
as maintained by Strasburger, the nucleus of the produced cell, — not
the nucleolus, as claimed by Biitschli. It appears to enlarge at the ex-
pense of the small, clear mass to which it is Joined, after the corpuscles
which form it are united into a homogeneous mass ; the latter takes an
oval form, and becomes more and more regular. The substance of the
young nuclei are stained less by carmine and hematoxylin as the cell
enlarges. The body of the cell soon ceases altogether to be stained.
A résumé of this paper, together with those of Auerbach (’74), 0.
Hertwig ("75), and Strasburger (’75), has been published in the Quar-
terly Journal of Microscopical Science, by Priestley (76).
AUERBACH (’76) objects to considering the “ Kernspindel” as equiv-
alent to the nucleus. It corresponds to the middle part of the karyo-
lytic figure,* for the following reasons : —
(1.) Its volume is usually greater than that of the nucleus.
(2.) It does not have a sharp, but rather a very confused, limitation.
(3.) It is to be found only at the time of, or after, the disappearance of
the old nucleus. It demands the use of chemical reagents to make a dif-
ferentiation within its substance apparent. This structural appearance Is
the optical expression of regulated morphological conditions under which
the commingling, and subsequently the separation, of the two substances
proceed, — the expression of inequalities in their distribution, — and
indicates, on the other hand, those molecular displacements which are
incident upon the progressive elongation of the whole (figure). Toward
the end of the process there is formed in the equatorial plane, owing to
an elimination of the nuclear sap in the direction of the poles, a more
* ‘‘Der bewusste lingsstreifige Korper ist nicht der Mutterkern, sondern der Mit-
teltheil der von mir sogenannten karyolytischen Figur, also ein Product der Ver-
mischung der eigentlichen Kernsubstanz mit dem umgebenden Protoplasma.”
MUSEUM OF COMPARATIVE ZOOLOGY. 305
compact transverse layer. This persists, and as a wall of separation
prevents the fusion of the two new nuclei which arise near each other in
the handle of the dumb-bell figure.
(4). It is not fully, nor even principally, composed of ‘ Kernsub-
stanz,” for its principal mass does not enter into the formation of the
new nuclei.
Furthermore, the new nuclei do not arise by the division of a mother
nucleus. The substance of the striate body (spindle) does not enter
into the formation of the new nuclei, but the latter are differentiated
only at the poles of the spindle body, as two relatively small, spherical,
clear, and homogeneous bodies, which, at times, are seen to be formed
by the confluence of smaller drops, and therefore evince their origin as
collections of previously distributed substance. The greater portion of
the spindle structure is not transferred to the new nuclei, but merges
with the protoplasm, and even lies in the periphery of the daughter
cells, where it helps to form (plants) the cellulose membrane. The
striate body is a structure combined out of nuclear substance and cell
protoplasm, which latter has made its way in from the sides.
The evidences of the formation of the spindle within the still per-
sisting nuclear membrane (see especially O. Hertwig’s studies) are too
numerous and unequivocal to allow any doubt in the cases presented.
I cannot but believe, however, that the exact size of the spindle, as
compared with that of the nucleus, has little to do with the question of
a dissolution of the whole nucleus. A total disappearance of the old
nucleus is, of course, the cardinal point. I have never found a stage in
which nuclear substance was not demonstrable by staining, and agree
with those writers who derive the new nuclei primarily from the halves
of the nuclear plate, — I even doubt if the poles of the spindle (or the
corpuscles of the central ‘‘areas”) take any direct share in the composi-
tion of the new nuclei.* Of this latter point, however, I am not fully
persuaded. It is possible that the increase in the size of the young nu-
cleus may ultimately bring its periphery in contact with these corpus-
cles, while the latter are still intact, and that they may then directly
contribute to the formation of a nuclear membrane. I am, however,
more inclined to think the corpuscles cease to exist as discrete struc-
tures before any such event could transpire, and that they contribute
less directly, if at all, to the substance of the nuclear mass.
Another paper by Auerbach, directed principally against views enter-
tained by Strasburger, is considered in another connection (p. 370).
* See also the objections raised by Flemming (78%, p. 415).
‘VOL. VI.— No. 12. 20
306 é BULLETIN OF THE
In his work on the development of Elasmobranch fishes Batrour (76,
pp. 393-402, and ’78, pp. 15-24, Pl. II.) has figured and described
some interesting observations on the changes of the nucleus during seg-
mentation. The earlier stages of cleavage did not afford information —
in this direction, but when the segments had become numerous, and
in diameter between 0.25™™ and 0.08™™, it was observed, in sections of
specimens hardened in chromic acid, that the place of the nucleus was ,
occupied by a sharply defined figure having the shape of two cones placed |
base to base, which stained as deeply as a nucleus. ‘From the apex
of each cone there diverge toward the base a series of excessively fine
strie. At the junction between the two cones is an irregular linear
series of small deeply stained granules, which form an apparent break
between the two. The line of this break is continued very indistinctly
beyond the edge of the figure on each side. From the apex of each
cone there diverge outwards into the protoplasm of the cell a series of
indistinct markings. They are rendered obscure by the presence of
yolk spherules, which completely surround the body just described, but
which are not arranged with any reference to these markings.” |
The course of the markings (loc. cit., Pl. II. Fig. 7a), which evidently
correspond to asters, is quite unlike anything observed by others ; if not
fundamentally, at least in the extent of the deflection which the lines
suffer, causing, as it does, the most of them soon to take a course almost
parallel with the sides of their respective cones. I recall nothing similar
to this appearance, unless possibly the fibres which Strasburger (76,
p. 45) describes as resulting from a resolution of the ‘‘mantle” of the
cask-like spindle into filaments in Spirogyra may be comparable to it.
In the present case, however, the “markings” do not form fibres continu-
ous from pole to pole. Balfour justly calls attention to the fact that the
strive of the cones are not to be confounded with the markings, for the
cones are quite as distinctly differentiated from the cell as nuclei are,
whereas the “markings” are merely structures in the general proto-
plasm of the cell.
The end view of the spindle given by Balfour (Fig. 7 6) affords no idea
of the real distribution of the “linear series of granules,” which repre-
sents the nuclear plate. The colored circular body in each cone, which
he once observed, —after a line indicating cell division had made its
appearance in the plane of the base of the cones, — may possibly rep-
resent the lateral zones of thickenings ; the drawing (Fig. 7 c), however,
leaves room for doubt.
The important observation is made by Balfour that these conelike
MUSEUM OF COMPARATIVE ZOOLOGY. 307
bodies are not only found in the cells of the germinal disk, but also in
the yolk completely outside the disk. From this the author concludes
that these bodies can occur where their connection with cell division is
altogether out of the question, — where, in their changes, they are with-
out any influence on the surrounding protoplasm.
In later stages of segmentation the conelike bodies are less frequently
met with, notwithstanding the fact that the nuclei are more numerous,
and are increasing in number more rapidly than during earlier stages.
Other bodies are seen, however, which are intermediate between them
and ordinary nuclei. Of the three figures (8 a—c) given of these inter-
mediate structures, one (8 a) is evidently a spindle in which the nuclear
plate is about dividing, and another (8 ¢) is a more advanced stage, while
the third is not so easily referable to known stages in the metamorphosis.
Balfour affirms that the granules contained in these bodies exactly re-
semble the granules of typical nuclei. All these bodies occupy the place
of, and stain like, ordinary nuclei, and are as sharply defined. The
true nuclei of the germinal disk are for the most part regularly rounded ;
_ those of the yolk are often irregular in shape, and provided with knoblike
projections, indicative of a process of division in the primitive nucleus.*
In no case is a distinct membrane to be seen around any of the nuclei.
Balfour’s conclusions, drawn from a comparison of his results with
those of other observers, may be reproduced in his own words : —
“Tn the act of cell division the nuclei of thé resulting cells are formed
from the nucleus of the primitive cell. This may occur, —
“(1.) By the complete solution of the old nucleus within the proto-
plasm of the mother cell, and the subsequent reaggregation of its matter
to form the nuclei of the freshly formed daughter cells ;
“(2.) By the simple division of the nucleus ;
“(3.) Or by a process intermediate between these two where part of
the old. nucleus passes into the general protoplasm and part remains
always distinguishable and divides; the fresh nucleus being in this case
formed from the divided parts as well as from the dissolved parts of the
old nucleus.”
A series of all possible gradations between the first and second, may
be embraced under the third.
Balfour’s conception of the cause of the stellate figures is more me-
chanical than that of Auerbach, whom he in the main follows. The
Streaming out of the protoplasm of the nucleus into that of the cell will
* It is more likely that these projections are stages in the confluence of several
vesicles to constitute a nucleus.
308 BULLETIN OF THE
be accompanied by the formation of a wake on the peripheral side of
such large granules as cannot be displaced. Any granules carried by
the current into this wake will remain there, and thus contribute to the
formation of a radial row of granules, and a series of such rows would
produce an appearance of striation.
The conclusions drawn for Elasmobranchs are, that in the earlier
stages of segmentation, and during the formation of fresh segments, a
partial solution of the old nucleus takes place, but all its constituents '
serve for the reconstruction of the fresh nuclei ; that in later periods of
development a still smaller part of the nucleus becomes dissolved, and
the rest divides, but that the two fresh nuclei are still derived from the!
two sources ; and, finally, that after the close of segmentation the fresh
nuclei are formed by a simple division of the older ones.
Lupwie (76, p. 484) believes that in the development of spiders’ eggs
the increase in the cells may be accompanied by nuclear changes such
as have been observed by Fol, Biitschli, and others. Evidence of this
is to be found especially in the radial direction of the deutoplasmic ele-
ments in the separate cell territories and the appearance of the nucleus
in the centre of this radial structure, as well as in the fibre-like (strang-
artig) connection of two recently separated centres.
The origin of the nuclei (p. 476) was not satisfactorily made out. In
one case the nucleus seemed to arise by a fusion of a number of small
round structures, in which case the central mass assumed a foamy ap-
pearance which disappeared as soon as the nucleus became visible. One
might conclude that the nucleus arose by a fusion of the vacuoles which
caused the foamy appearance, were it not for the fact that the vacuoles
were sharply — the nucleus only indistinctly — outlined.
The fusion of the deutoplasmic balls into columnar structures, and the
radial arrangement of the latter (p. 474), the author refers not to any
subjective activity of the deutoplasm, but considers as a passive phe-
nomenon brought about by the active vital processes in the protoplasm.
In his book on Zellbildung und Zelltheilung, STRASBURGER ("76) availed
himself of the then recently made observations on cell division by Auer-
bach, Biitschli, and others, to show the prevalence of the phenomena
observed by him to take place in plants. To these evidences he adds
(pp. 208-231) observations of his own. Those relating to the changes
occurring in the cell division of cartilage are considered in another
connection. His other observations were made on the eggs of Phallusia
mammillata and Unio pictorum.
In artificially fecundated eggs of Phallusia the nucleus of the first
MUSEUM OF COMPARATIVE ZOOLOGY. 309
segmentation sphere immediately upon its formation is surrounded by
a homogeneous ‘ Plasmazone,” and by rays traversing the contiguous
granular protoplasm. The rays increase in length as the nucleus, with
gradually retarded velocity, moves from the periphery to, or near to, the
centre of the egg. The nucleus, at first homogeneous, increases in size
after its migration, and becomes less refractive ; the rays and “ Plasma-
zone” disappear. The nucleus becomes indistinct, and it can be shown,
by the use of reagents (p. 213), that it becomes spindle-shaped, streaked,
and acquires an equatorial ‘“‘Zellplatte ” [Kernplatte?]. However, in liwing
eges (p. 217) one can see that the arrangement of the plasma becomes
radial to the two poles of the nucleus about to divide, and more distinct
as soon as the segments of the nuclear plate separate, — Auerbach’s kary-
olitic figure. If, at the beginning of the division, the nucleus remains
eccentric, the whole figure moves toward the centre of the egg. The
“ Kernfaden ” [interzonal filaments] are not numerous, and become in-
distinguishable before completed division.
It may be observed in Limax that the filaments remain visible longer.
I think their early disappearance in Phallusia may have been due to the
nature of the reagent (osmic acid) used by Strasburger, rather than to
any difference in the eggs.
The rays increase in length as the formation of the new nuclei advances,
till they reach the periphery and equatorial plane ; the egg lengthens in
the direction of the line uniting the new nuclei; the equatorial plane be-
comes clearer. An annular constriction, beginning on all sides at the
same time, appears, and the division is accomplished so quickly as to
seem simultaneous throughout its whole extent. The rounded segmen-
tation products become mutually flattened.
The nuclear metamorphosis, as demonstrated by reagents, is the same
as in Unio (see below). The author believes he has now and then seen
slight thickenings (Zellplatte) in the equator of the interzonal filaments
similar to those observed in plant cells, and thinks they may arise from
the ‘‘Hautschichtmasse” collected in the plane of division ; he also sug-
gests a similar interpretation for Fol’s figure of the Pteropod egg, but, as
has already been indicated (p. 292), it is probable that the figure in
question represents a stage antecedent to the formation of the nuclear
plate, and hence can hardly bear the interpretation proposed by Stras-
burger. As the second division is being initiated, it sometimes happens,
under abnormal circumstances, that the two segmentation cells formed
by the first division again fuse. In eggs thus artificially made uni-
cellular, there may be distinguished four suns united in pairs by con-
necting bands.
310 BULLETIN OF THE
Owing to the opacity of the cells in Unio (pp. 213-216) they were
studied with the aid of sections. Only embryos consisting of about
twenty cells were used. The nuclear plate is found by study of cross
sections to be formed, not of an annular series of granules (Korner-
kranz), but by a continuous disk (durchgehende Kornerscheibe). The
author does not mention any inequality in the distribution of the
granules, such as is exhibited in Limax, nor does his figure (doc. cit.,
Taf. VII. Fig. 18 6) make the granules of the ‘“ Kernplatte” more con-
spicuous than those of the surrounding protoplasm. The poles of the
spindle are much more marked, on account of their great refractive
power, than in plant cells. The rays of the protoplasm converging
toward them are very distinct in animal cells, hardly traceable in plant
cells. The two segments resulting from a division of the nuclear plate
are found in different cells at varying distances from each other. In-
terzonal filaments are neither increased in number, nor suffer a lateral
expansion, as in plant cells. In some of Strasburger’s figures (e. g.
Taf. VII. Fig. 20) both ends of the spindle appear broadly truncate after
the separation of the segments of the nuclear plate, and each trun-
cate face occupying the centre of its aster is marked by a conspicuous
structure in which the nuclear fibres terminate.
Following this condition is a stage in which the new nuclei are homo-
geneous. The latter never occupy the centre of the sun, but often ro-
tate, as it were, about the former pole without reaching it. In this way
two contemporaneously formed nuclei may eventually lie (as in Stras-
burger’s Fig. 10, Taf. VIII.) farther apart than the centres of the two
asters. In all animal cells which he has had the opportunity of study-
ing, Strasburger finds that the new nucleus becomes at first homogene-
ous by the confluence of all the components‘of each half of the maternal
nucleus (p. 226), that its definite formation beginning on the side toward
the equatorial plane advances to the poles, and that the portion defi-
nitely perfected (equatorial portion) is distinguishable from the more
homogeneous by its low power of refraction and by its nucleoli ; further,
that this equatorial portion has generally been taken for the whole nu-
cleus. The nucleus may arise by the union of two closely situated vacu-
oles, but a greater number than two had never been seen. At the time its
definite formation (Ausbildung) is completed, the nuclei are more or less
pear-shaped, with the pointed ends occupying the centres of the asters.
The rays disappear; the nucleus becomes rounded and a membrane is
formed ; it still continues to enlarge, probably taking its food from the
surrounding homogeneous protoplasm (pp. 219-221).
MUSEUM OF COMPARATIVE ZOOLOGY. ool
When the products of the division cells are of unequal size (as in
Unio), the “ Mutterkern” takes an eccentric position, so that the plane
of division is equidistant from the new nuclei. If one sede of the spindle
lie nearer the surface of the cell than the other, the constriction of the
protoplasm begins earlier on that side of the cell.
Strasburger criticises O. Hertwig’s description of the nuclear spindle
as a band, since it is really cylindrical, and is shown to be so by Hert-
wig’s own observations. He in turn admits the justice of Hertwig’s crit-
icism when the latter claims that the nuclei do not arise in Phallusia (as
Strasburger first reported) at the centre of the asters. Both Auerbach
and O#Hertwig have, he says, overlooked the homogeneous portion of
the young nucleus, which reaches to the centre of the sun.* The inter-
zonal filaments, like the nuclei, are susceptible of being nourished, and
are thereby often considerably increased in mass and numbers, especially
in the equatorial plane.
The general and theoretical considerations announced by Strasburger
will be considered in connection with the review of his studies on plant
cells. }
Zewuer (76, p. 258, Taf. XVIII. Figs. 26-31) describes for Polysto-
mum integerrimum remarkable changes in the nuclei during segmenta-
tion. After the two nuclear structures (pronuclei) have united, the
resulting body disappears, and at two opposite poles of the egg there
arise near the surface two clusters of vesicular nuclei with nucleoli.
These nuclei increase in number and in size. Approaching each other
closely, the components of each cluster are at length dissolved into a
homogeneous mass. The cell now changes its form, elongating in the
direction of the axis which joins the two clear poles, and finally from the
more pointed end there grows out a bud which is ultimately pinched off.
The single cell is thus divided into two cells of unequal size.
The most natural interpretation to be given the clusters of nuclei is
that they are the same as the clusters seen by Biitschli and other ob-
Servers to result from the metamorphosis of the “nuclear plate” of a
spindle, although nothing like a spindle figure was seen by Zeller.
* In Limax I have seen the nucleus deviate considerably from the spherical form,
and appear as though drawn out toward the centre of the aster (Fig. 80%, compare
also the pronuclei, Fig. 68) ; but there is nothing which gives support to Stras-
burger’s view that a homogeneous portion of the nucleus reaches to the centre of the
sun. Iam even inclined to think that Strasburger may have fallen into an error in
the case of Unio, by mistaking granules at the centre of the sun for evidence of a
continuation of the outline of the nucleus to that point.
312 BULLETIN OF THE
Their great number and enormous size as compared with that of the
cell, their nearness to the surface, and their diffuse arrangement, com-
bine to make this an interesting case of nuclear reconstruction.
Ep. van BENnEDEN (764, pp. 38, 47-52) discovered in one of the two
forms of the parasitic Dicyema certain spherical striate bodies. These
were always found in the vicinity of the germarium (germigétne), and in
size were, when occurring singly, like the germs. These were for a time
thought to be spermatophores, but the author’s attention was at length
directed to their similarity to the nuclei of dividing cells as described
by Biitschli and Strasburger. They were ultimately found to be germ
cells in process of division. Immediately before dividing, says Van Be-
neden, the germ (a single cell) becomes very granular and opaque; the
nucleus increases considerably in size, its contents lose much of their
transparency, and its nucleolus disappears; then an extremely clear,
meridional striation is developed at the surface of the nucleus; the strize
are not the result of an alignment of corpuscles or granules, but are due to
the presence of continuous, homogeneous fibrils, formed of a very refrin-
gent substance. If one of its poles is directed toward the observer, this
striation appears radial. The volume of the nucleus increases at the
expense of the surrounding protoplasm to such an extent that the latter
is reduced to a thin layer of granular substance enveloping the former.
There soon appears at each pole of the nucleus a refringent “ corpuscle
polaire,” around which are grouped very fine granules. The two poles
become differentiated into granular polar disks, in which the ends of the
meridional fibres are lost. At this time a polar view shows that the
radial strize are somewhat curved (PI. I. Fig. 28, Pl. III. Fig. 3), — much
as the wtelline rays are in Limax (Fig. 56),— proof that the fibres do
not exactly follow the direction of meridional lines, but are a little —
oblique. The fibres exist only at the surface of the nucleus. The polar
disks become thicker, more refringent, and distinct ; the fibrils less clear,
as if their substance were attracted toward the poles. The author has
but rarely met with fibrils a little thicker in the middle than elsewhere ;
aside from this, he has seen no indication of either equatorial or lateral
nuclear plates. Later, the polar disks are in some way condensed into
small, discoidal, refringent bodies (pronucleus dérivé), around each of
which is accumulated in the protoplasmic body a clear substance from
which radial [extra-nuclear] striz are sometimes seen to diverge (pronu-
cleus engendré), The Zellplatte of Strasburger appears in the equator
as a dark granular plate; a circular furrow appears at the equator of
the cell; the cell-plate divides into two; the two hemispherical cells
MUSEUM OF COMPARATIVE ZOOLOGY. at
remain in contact by that part of their surfaces which is developed by
the division of the cell-plate. The ‘pronucleus dérivé” increases by
blending with the “ pronucleus engendré.” The part of the old nucleus
which remains striate and non-granular continues adherent to the cell-
plate. The young nucleus enlarges, becomes clearer and more central
in position, its contour regular, and it acquires a small nucleolus. Finally
the last trace of the striated part of the old nucleus disappears.
Rast (76, p. 318) often observed a karyolitic figure, especially in eggs
(Unio) hardened by chromic acid, but is unable to give any account of
the nuclear division itself.
In Bopretzky’s ‘Studies on the Embryonic Development of Gastero-
poda” (’76), some attention is given to the changes of the nucleus dur-
ing segmentation, especially in the case of Nassa mutabilis, Lam. (pp. 97 —
102). Usually the nucleus is not to be found after the egg is laid, but
in one instance, by employing pressure, it became visible immediately
under the surface of an egg which had already given rise to polar glob-
ules. Its contents had a homogeneous, water-clear appearance. Subse-
quently, there is a lengthening of the egg in the direction of the diameter
passing through the formative pole, and, following this, a constriction in
a plane at right angles to this diameter. At this time no nucleus is
discoverable in either half of the incompletely segmented egg. Thin
sections through the upper (or formative) half of specimens hardened in
chromic acid exhibit the radial figures seen by Fol and others. In the
middle of the finely granular substance are to be seen two clear spots
without granules, from which there diverge toward the periphery rays
which are formed of granules abutting upon each other to form straight
lines. Those of the rays which are directed from the two centres toward
each other unite midway between the spots, and such as lie on either
side of a line uniting the latter are more or less curved. In the middle
this system of curved lines is interrupted by a very narrow streak of
highly lustrous granules, which are somewhat coarser than those compos-
ing the balance of the lines. This is Biitschli’s spindle and its equatorial
zone. Although on sections, the spindle stands forth somewhat more
sharply than the radial rays, and is a little more intensely stained in
indigo-carmine, yet it is of quite the same nature. Not only is there
no nuclear membrane, as Biitschli thinks, but, says Bobretzky, “I cannot
distinguish in it [spindle] the actual fibres, which, just like the rays, are
nothing else than serially arranged granules.” The appearance of two
radial centres precedes the origin of the spindle-shaped body. In later
Stages of segmentation the two stars were already to be seen when the
314 BULLETIN OF THE
nuclei were still almost unchanged (see also op. cit., p. 108, Fig. 29 B. n).
The author thinks he has seen, on sections of an egg presenting the
first traces of the [first or] transverse furrow, the disappearing nucleus
in the shape of a pale, hardly visible body midway between the two stars.
It is described as an elongated, roundish, clear space, which differs only
very slightly in its optical properties from the surrounding protoplasm,
and is especially distinguishable only by the fact that the rays of the
two stars which traverse it are interrupted at its boundaries. The lim-
its of this space are thus clearly indicated by granules somewhat larger
than those which compose the rays (Fig. 24).
It is with reluctance that one ventures to impeach the accuracy of
another’s observations, especially if the observer is one of such broad
experience as Bobretzky ; and yet I am convinced that his “ disappear-
ing nucleus” is in reality nothing more or less than the “nuclear disk”
seen obliquely, — not edgewise, as in Fig. 23. The means of settling the
question lay of course in the hands of the observer, for the two sides of
the oval body could not have occupied the same niveau, if my interpreta-
tion is correct, and I confess it seems difficult to understand how this
could have been overlooked by so competent an observer. It becomes
all the more difficult to understand when, further on,* Bobretzky says
that possibly the refractive granules surrounding the nucleus may be
coordinated with the transverse granular band seen in the preceding
figure. That the two are really the same structures, I have not the least
doubt ; but the author’s attempt to explain their relation to each other
cannot be regarded as successful. It is in accordance with an erroneous
view of the origin of the median zone that he would interpret the mean-
ing of this figure in case he is compelled to grant that its surface gran-
ules are identical with those of the transverse granular band. In that
event, he says, one would be justified in drawing the conclusion that —
in direct opposition to Biitschli’s view — the granular zone (Fig. 23) is
formed out of two rows of granules, which approach each other and unite
in the middle of the [in the mean time] dissolved nucleus. That such
an approach of granules takes place is based on the assumption that the
egg drawn in Fig. 24 is less advanced (younger) than that drawn in Fig.
23, for a direct observation of the approach is not claimed. ‘This as-
* “|. , vielleicht wire es méglich, die an den Grenzen des Kernes befindlichen
glinzenden Korner mit dem queren Kornerstreifen der vorigen Figur gleichzustellen,
woraus man den Schluss ziehen diirfte, dass die aequatoriale Kérnerzone sich, der
Meinung Biitschli’s ganz entgegengesetzt, aus zwei, sich einander nahernden und in
der Mitte des aufgelésten Kerns zusammentretenden Kornerreihen bildete.” (p. 100.)
MUSEUM OF COMPARATIVE ZOOLOGY. ala
sumption in turn is supported by only two statements: the presence
of the supposed nucleus in Fig. 24, and the slight development of
the transverse constriction which affects the first segmentation (Fig.
24. f).
The appearance which the author has interpreted as a nucleus admits,
as has just been suggested, quite a different explanation, which I shall
directly attempt, to strengthen by further evidence. As regards the
second argument, — the shallowness of the constriction, —a compari-
son of Figs. 23 and 24 does not, owing to the incompleteness of the
outlines, give satisfactory proof of the author’s position ; but a compari-
son of Fig. 1 (the egg from which the section shown in Fig. 23 was made)
with Fig. 24 certainly leaves the impression that the constriction is, as
the author claims, less advanced in the latter than in the former case,
and that consequently the egg seen in Fig. 24 is probably younger than
that shown in Fig. 23. I am, however, more inclined to agree with
Bobretzky as to the relative advancement of the two eggs, on account of
evidence which he does not seem to have given special consideration. I
refer to the fact that in Fig. 23 the granular zone appears to be com-
posed of halves which are separated by an appreciable interval, while in
Fig. 24 the zone appears (according to my interpretation of the figure)
still undivided. Granting that Fig. 23 represents a more advanced egg
than Fig. 24, it by no means follows that the mutual approach of the
rows of granules is the only possible explanation of the phenomena.
Not only is it posseble to refer the appearance to the obliquity of the
granular zone, but I think a careful examination and comparison of the
figures will show that this latter is much the more probable interpreta-
tion. Assuming that such a spindle-shaped body were viewed, not per-
pendicularly to the axis, but obliquely, a shortening of its apparent length
would result. That is what is found.to be the case in comparing the
spindles in the two figures cited, that of Fig. 24 being shorter than that
of Fig. 23 by about one tenth the length of the spindle. If, in answer to
this, it were objected that the anterior segment of the egg itself is also
somewhat smaller in Fig. 24 than in Fig. 23, and that consequently the
shortness of the spindle is the result of the diminutive size of one of the
eggs, I would suggest in reply, —
(1.) That there is a greater proportionate reduction in the length of
the spindle than in the width of the egg ;
(2.) That the diminished width of the anterior end of the egg might
also be produced by the same obliquity ; for it is reasonable to suppose,
from what is known of the shape of other eggs at this stage of develop-
316 BULLETIN OF THE
ment, that an elongation of the blastomere itself has taken place in the
direction of the axis of the spindle ; and
(3.) That both spindles have the same thickness at the middle, (the
apparent thickness being unchanged by the supposed obliquity,) which
would not be expected if the spindles differed considerably in size.
Although the observations made on Limax add another case to those
where the stellate figures certainly arise before the disappearance of the
nucleus, I think it will be difficult to show any case which shall justify
the conclusions drawn by Bobretzky from his studies on the origin of
the spindle; certainly his own figures do not warrant him in saying:
“Obschon der Kern wenigstens in seiner iusseren Form noch unverin-
dert erscheint, kann man schon hier den sogenannten spindelférmigen
Korper unterscheiden, dessen Entstehung also keineswegs auf eine Um-
wandlung des Kerns zuriickzufiihren ist.”
I must especially insist upon the insufficiency of Bobretzky’s observa-
tions to establish this assertion. The statement is evidently based on
such stages as those shown in Figs. 24 and 29. n. .I have given above
what seems to me a more reasonable interpretation of his Fig. 24, and
have only to add that Fig. 29. 2, although showing at the same time
the nucleus with a nucleolus and the two stellate figures, does not ex-
hibit the least trace of interstellate rays, — a spindle, —so that it ©
does not afford any ground for the assertion, that “the origin of the
spindle-shaped body is in no way referable to a metamorphosis of the
nucleus.” |
Respecting the new nuclei, Bobretzky states, that they are to be dis-
covered as small bodies connected by fine granular lines as soon as the
segmentation furrow, which is to separate their respective cells, makes
its appearance (Fig. 25); that subsequently the nuclei have become larger
and the nuclear commissure has become almost invisible (Fig. 26). Ac-
cording to this latter figure the commissure is more conspicuous in the
middle than near the nuclei, just as I have found it to be in Limax, ex-
cept that the striate appearance is not at all represented in Bobretzky’s
figures.
Of the method in which the nuclei are formed, the author is not able
to say anything very definite. In the stages just mentioned, he believes
he has seen in the clear central spot of the stars an accumulation of very
small pale vesicles, from which one might deduce the formation of new
nuclei. No reconciliation of this untenable assumption with the accurate
observation recorded in the following sentence is attempted. Bobretzky
saw, namely, in one case clearly (Fig. 29 B. m) two new nuclei in addi-
re >
MUSEUM OF COMPARATIVE ZOOLOGY. Billy
tion to the stellate figures, and that they did not occupy the centres
of those figures, but lay somewhat nearer each other (p. 108).
After careful examination the author comes to the conclusion that the
large nutritive segment is destitute of a nucleus, and therefore refuses
to acknowledge that it is a cell. It is only a detached portion of the
nutritive yolk.
The final paper from Burscuii (’76), portions of the substance of
which had already been made public in the two preliminary communica-
tions that have been passed in review, embraces a wide field of observa-
tion, and presents important additional information upon the phenomena
connected with cell division.
In the case of Nephelis (p. 219) the stellate figures about the poles of
the spindle receive an attention not accorded them in the preliminary
papers. Around each of the ends of the first spindle (Richtungsspindel)
is to be seen a clear area (Hof), distinguishable from the remaining
yolk mass by its homogeneous condition, from which the yolk granules
stretch out radially through the yolk in all directions, — “ ein Strahlen-
system oder eine Sonne.” The clear area possesses no definite boundary
toward the granular yolk, byt merges gradually into it (p. 216).
The nucleus of the first segmentation sphere exhibits a distinct, dark
envelope (Hiille), and embraces no nucleoli, but instead a clear fluid which
is traversed by a number of protoplasmic cords which enclose here and
there dark refractive granules, and which are often united into a network.
The first segmentation is introduced by an elongation of the yolk and
the metamorphosis of the nucleus into a spindle. At each of the oppo-
site points of the nucleus which fall in the axis of elongation, there arises
in neighboring parts of the yolk a radiation, and at once there begins to
appear in the centre of each a clear area of the kind just described.
Between these two points the nucleus now begins to undergo a longi-
tudinally fibrous differentiation. While this differentiation advances,
the still unaltered nuclear remnant continues to exhibit, though less
distinctly, its previously described structure, till it at length completely
disappears. The volume of such a spindle-shaped metamorphosed nu-
cleus is less than that of the original. The change, in Biitschli’s opin-
ion, can only be explained by supposing that a portion of the fluid of
the nucleus escapes during the metamorphosis.
I pass over points already reviewed in the preliminary papers, and
only add that Biitschli saw the fibres of the Kernspindel again become
thickened and darker in the equator after the beginning of the segmen-
tation, and thus form the so-called cell plate of Strasburger (p. 219).
318 BULLETIN OF THE
The metamorphosis of the primary segmentation nucleus into a spin-
dle was not so satisfactorily traced in the case of Cucullanus elegans.
Possibly a stage in this change is represented, says the author, in Fig.
20, where, in place of a nucleus, there is only an indistinctly defined
clear spot in the centre of the yolk, within which spot a number of dark
granular rods are irregularly disposed. This and all subsequent spindles
differ from the “ Richtungsspindel” in that the rods of the nuclear plate
in the former lie within a definitely limited body, and cannot therefore
be simply a differentiation in the yolk (p. 224), while in the latter the
nuclear plate is formed of only a circle of dark granules (p. 226).
When the new nuclei have made their appearance in the place of the
lateral plates, the nuclear fibres are no longer to be seen. Each nucleus
arises from a few (two to four) separate nuclei, which subsequently
unite. <A distinct nucleolus is found only at a much later stage. The
radial structure of the yolk is to be seen during segmentation, as in
other eggs, but on account of the extremely fine-granular nature of the
yolk it is relatively difficult of observation.
In his studies on the gasteropods Limneus and Succinea, one looks
for a close agreement with the phenomena which take place in Limax.
The division of the primary segmentation nucleus begins in the still
spherical yolk by the appearance of two small radial systems at diamet- —
rically opposite points of the nucleus, which determine the axis of the
subsequent division.
In Biitschli’s Fig. 10, Taf. TV., which is here cited, one sees that the
stellate figures arise at points on the nucleus which are not, strictly
speaking, diametrically opposite, but rather somewhat nearer the centre of
the egg than is the centre of the nucleus ; just as we have seen in Limax
that the asters are somewhat deeper than the centre of the two pronuclear
structures taken as a whole. The centre of each star is occupied by a
homogeneous clear area. Since acetic acid was used by Biitschli, it is
not strange that a central, more refringent structure was overlooked.
Other reagents would doubtless have disclosed the fact that this area is
not entirely homogeneous. In a subsequent stage (Fig. 11) the nucleus
has assumed a streaked appearance. At first the dark interior corpus-
cles of the nucleus are visible between the streaks, but they soon disap-
pear, and the nucleus becomes a longitudinally striate spindle, stretching
between the two suns. Biitschli has figured (Fig. 13) an egg in which
the constriction of the yolk is conspicuously advanced, and in the mid-
dle of the spindle are seen fibre-thickenings, which he considers to be
the nuclear plate. Although it is hardly safe to infer from a comparison
|
MUSEUM OF COMPARATIVE ZOOLOGY. 319
with observations on Limax that these thickenings represent the cell
plate, and that the young nuclei have been overlooked, nevertheless, if
this is not the case, there must evidently be a want of synchronism in
the events of cleavage in the eggs of these two gasteropods, for at a
nearly corresponding stage of segmentation in Limax (Fig. 90) the
halves of the nuclear plate are already far apart. That, however, which
seems to render the first supposition almost certain, is the fact that the
testimony of other observers who have carefully studied these stages leads
to the same conclusion. I will call attention to the statements of Hert-
wig (75, pp. 409, 410, Fig. 25) and Bobretzky (’'76, p. 101, Fig. 25),
and to the fact that Biitschli’s own figures of Succinea (Taf. IV. Fig. 19),
Cucullanus (Taf. III. Fig. 21), and Nephelis (Taf. I. Fig. 12) point to
the same conclusion. It is to be noticed further, in regard to the last-
mentioned figure and its explanation, that the author places himself in
an ambiguous position, unless ‘‘ Xernplatte,” in the statement, “ Die
sogennante Kernplatte ist gebildet,” is a misprint for Ze//platte.*
The author informs us that he has not observed the separation of the
halves of the nuclear plate, from which I conclude that he has not ob-
served any stages showing the halves of the plate, for he has given no
such figures, and a dvrect observation of the migration is hardly to be
thought of in such opaque eggs. The new nuclei are also in this case,
without doubt, formed by a differentiation of the halves of the nuclear
plate which have migrated into the ends of the spindle. Where they
have already appeared (Taf. IV. Figs. 14, 19) one sees clearly that the
fibres which join them are again swollen in the middle and have become
dark and lustrous. I am at a loss to understand the figures given by
Biitschli in this connection. They correspond in no way, as far as re-
gards the shape and appearance of the thickened portions, with anything I
have seen. Ifthe fibres of the lower half of the spindle represented in
Fig. 19 were slightly thickened in the middle, and the upper half were
entirely absent, the figure would very closely correspond to what I have
many times seen in Limax. The nuclei increase in size and remain
united by the interzonal filaments when the segmentation is otherwise
completed. The author did not observe what became of the cell plate.
The phenomena presented by Rotifera agree very well with the obser-
* Since writing the above I observe what had escaped my notice before, — that
Biitschli has expressed, in his explanations of Taf. IV. Fig. 13, a doubt as to this
structure being after all a nuclear plate. It seems to me that, with the material at
command, he might have expressed himself even more decidedly in favor of its being
a cell plate.
320 BULLETIN OF THE
vations on Nephelis. In Brachionus (p. 247) the radial figures appear
suddenly in the yolk at two opposite points of the nucleus, and at each
of these places is formed a re-entrant surface. These surfaces advance
till they meet, and thus seem to cause the disappearance of the nucleus.
The process, however, as acetic acid preparations show, is only a nuclear
metamorphosis, which advances from the points mentioned. The division
of the nuclear plate and the migration of its haives was observed in No-
tommata. In the two genera mentioned, only a single new nucleus is
formed in each new segment. Why Biitschli cites in this connection
Flemming’s (75, Taf. III. Fig. 2) figure of Anodonta as making probable
the ultimate discovery of a cell plate in the Rotzfera, I cannot conjecture,
unless he made the mistake of supposing that the figure above cited was
that of a rotifer’s egg. Biitschli remarks, with reason, that he has never,
even in the rotifers, seen the new nuclei in the centre of the stellate
figure, as Flemming has drawn them in the case in question.
In a pseudovum of Aphis, Biitschli also once saw two small nuclei joined
by delicate filaments. The nuclei of the blastoderm, he therefore con-
cludes, arise by successive divisions of a single nucleus (p. 249). More-
over, the blastoderm cells of a butterfly and of Musca vomitoria (p. 261)
were demonstrated to present the striate spindle-shaped differentiation —
of the nucleus. In the former the equatorial nuclear plate was clearly
seen ; in the latter, only irregularly distributed local thickenings of the
spindle fibres. In Musca the radiation of the protoplasm about the ends
of the spindle was very distinct.
The second section of the fourth chapter of Biitschli’s paper (pp. 394-
419) is devoted to a general consideration of nuclear and cell division.
The author considers, with Strasburger, that the increase of nuclei by
means of a metamorphosis into a fibrous spindle-shaped structure is to
be regarded as the original and typical method. But there exists with-
out doubt another mode of nuclear division which greatly differs from
this, or at least may be referred back to it only by assuming very radi-
cal modifications (e. g. blood-disks of Rana, etc.). Supported by the
existence of a very delicate, yet exceedingly distinct membrane, envelop-
ing the nuclear spindle of the infusorian “nucleoli,” the author assumes
a similar membrane for all other nuclear spindles, and as evidence of his’
correctness calls attention to the distinct contour which was seen by
Strasburger to surround the nuclear plate of certain vegetable cells when
the plate was viewed en face. The indistinctness of the nucleus in the
living egg when it is undergoing its spindle metamorphosis the author
explains as due to three causes: (1.) the disappearance of the so-called
MUSEUM OF COMPARATIVE ZOOLOGY. sZk
nuclear membrane, whereby the nucleus loses its sharp limitation from
the protoplasm; (2.) a uniform distribution of the nuclear substance
through the whole nucleus; (3.) a loss of clearness. This last is attrib-
utable to a loss of nuclear fluid during the metamorphosis, which may
in the observed cases of Cucullanus and Nephelis amount to one third,
or even two thirds, the volume of the unaltered nucleus. What becomes
of this fluid (wisseriger Kernsaft)? It is not uniformly appropriated,
says Biitschli, by the surrounding protoplasm ; on the contrary, it may
be inferred — from the fact that the metamorphosis of the nucleus begins
at two points, and that each of the neighboring radial systems of the
yolk embraces a clear homogeneous central area, which is at first small,
and increases with the metamorphosis of the nucleus —that this fluid
escaping at these two points, as Auerbach maintains, becomes accumu-
lated in the central areas mentioned. So crude a conception of the origin
of the radial figures as Auerbach entertains cannot, he says, be accepted,
nor yet can Flemming be right in considering them due to a structural
condition of the protoplasm. First of all, the seat of the cause of the
radial phenomenon is to be sought in the central area. The latter, how-
ever, does not correspond to the end of the nucleus, and for this reason
Strasburger is at fault in referring the cause to an attraction which oper-
ates upon the surrounding protoplasm from the ends of the nucleus. For
the same reason the area itself cannot be regarded as a mass attracted
by the end of the nucleus. What may be the nature of the changes pro-
duced in the protoplasm of the area by the nuclear fluid, he is unable to
Say; perhaps it is only a simple swelling and solution resulting in the
homogeneous and light appearance of the area.
Aside from Biitschli’s failure to see a central structure in the area, it
seems to me that the optical properties of the latter — it being more
highly refractive than either the surrounding protoplasm or the nuclear
fluid —are not easily reconcilable with this interpretation.
The only deviation from a fusion, sooner or later, of the elements of
the nuclear plates, is that observed in the case of the primary nuclei of
Infusoria during conjugation. In the case of Paramecia, at least, the
plates retain their differentiated condition so that the fibrous, spindle-
shaped nucleus divides into two, each of which has a structure like the
original. |
Although a trace of a cell plate is to be found in Nephelis and snails,
it is unlike that found in plants, for there is no spreading out of the
nuclear fibres and the plate does not take part in the formation of the
cortical layer (Hautschicht) of the segments.
VOL. VI.— NO. 12. 21
B22 BULLETIN OF THE
It is admitted concerning the formation of the daughter nuclei out of
the halves of the nuclear plate, that in segmentation spheres the fusion
of the plate elements has not been established with-certainty. The
conclusion is reached, however, that the homogeneous and compacted
condition is the original and simplest form in which the nucleus appears,
quite contrary to Auerbach’s notion of a jlued cavity in the protoplasm.
So, too, the nuclear membrane is not produced from the protoplasm sur- —
rounding the nucleus, as Auerbach maintains, but, like the nucleolar
structures (Binnenkorper), is a differential product of an originally
homogeneous corpuscle. In Cucullanus, in Nephelis, and possibly in
snails, there are differentiated out of the nuclear plates at first several
small nuclei instead of one, each of which afterwards becomes for itself
differentiated into a vesicular nucleus, as does in other cases the single
nucleus.
This conclusion arises in part from Biitschli’s failure to recognize the
nature of one of the nuclear structures, the male pronucleus. But
aside from that, I have only to say that I have seen nothing of a like
nature in the case of Limax.
Much evidence of similar nuclear conditions is accumulated by Biitschli
at pages 409-412, in the course of which he mentions having seen
very distinctly in sections through eggs of Rana temporaria the radial
structure of the protoplasm around the halves of the “ Lebenskeime ”
(Gotte), when the latter had already advanced into the daughter cells, —
a phenomenon which escaped Gotte’s attention.
The more a daughter nucleus grows, the more the central area of ‘the
neighboring radial system diminishes, and the former gradually ad-
vances to the position of the latter, whence it is to be inferred that the
area furnishes the material for the growth of the nucleus; this consists
of fluid, and also of genuine nuclear substance. The nucleus acquires,
however, some of this nuclear substance by the retraction of the inter-
zonal filaments. When the growth of the daughter nucleus ceases, the
central area and the radiation have totally disappeared.
The want of precision, already noticed, in the account of the time
when the segmentation furrow appears, is, if possible, emphasized by
the author’s saying that the first trace of the division of the yolk appears
‘somewhere about the time” of the division of the nuclear plate and the
separation of its halves, —a period, I should say, of rather indefinite
duration, notwithstanding the rapidity with which the halves of the plate
begin to move asunder.
An important 7é6/e in cell division is to be ascribed, says Biitschli, to
:
|
|
)
}
|
|
6h
‘*
MUSEUM OF COMPARATIVE ZOOLOGY. pel
the nucleus; in many cases it is the immediate cause of the division,
and it is no contradiction of this that nuclear division may take place
without an accompanying cell division, for the field of its (nucleus) in-
fluence must have a limit. Most clearly does the nucleus sustain a
causal relation to the division in those cases where it is eccentric in
position, inasmuch as in these cases the segmentation invariably begins
on the surface of the yolk nearest to the nucleus.
The idea that the radial systems are due to centres of attraction, as
the author, together with others, once maintained, he is now inclined
to surrender, because it leaves the cause of the yolk division quite unex-
plained. He now maintains “that the radial arrangement of the plasm
around the central area is the expression of a physico-chemical altera-
tion of the plasm, emanating from the area, and that a gradual dimi-
nution of this alteration — which receives its support from the central
area — takes place from the central area toward the periphery.”
The assumption that the radial structure is of this nature is, in
Biitschli’s opinion, sufficient to account for the origin of an inequality in
the superficial tension of the sphere in case the chemical changes tend
to an éncrease of tension.* This tension will necessarily be restored to
equilibrium in accordance with the physical law that the superficial tension
is inversely proportional to the radius of curvature. As the maximum
tension will occur where the activities of the two centres combine (viz.
in the equator T), the equilibrium will only then be restored when the
radius of curvature at the equator is increased, and at the poles is
diminished. But this is equivalent to a prolation of the sphere. The
chemical changes continue, and as the prolation results in removing the
poles of the spheroid farther from their respective central areas, and in
bringing the latter nearer to the equator, the difference in superficial
tension must become exalted. A constant increase in the superficial
tension at the equator will result finally in an “ EKinfurchung” in that
plane, inasmuch as by this means the force of cohesion will be consider-
ably diminished by its outwardly directed negative component.
Aside from the author’s confessed inability to explain fully the subse-
quent “ Durchfurchung,” one feels impelled to inquire what ground
* The sphere obeys the fundamental laws of a fluid mass.
7 The author admits that this plane, as is evident, will be the equator only
under certain conditions relative to the rapidity with which the changes in the
plasm are propagated, but thinks that these conditions may well be assumed to be
present. On the other hand, it may be said that in Limax the stellate figures are
certainly not always synchronous in their origin, — that one may nave attained con-
siderable dimensions before the other is discernible.
324 BULLETIN OF THE
there is for the assumption that the physico-chemical changes result in
an increase rather than in a decrease of the superficial tension.
The author locates the causes of the metamorphosis of the nucleus
which finally lead to its division in the surrounding protoplasm, as Auer-
bach maintains, rather than in the nucleus itself. An evidence of this is
to be found in the fact that, if several dividing nuclei occupy the same
protoplasmic mass (Infusoria, etc.), they are found to present the same
stage of advancement. ‘This is, in his opinion, explainable by assuming
that the protoplasm acts alike and simultaneously on all the nuclei.
Although agreeing with Biitschli as to the location of the force which
induces nuclear division, I am not able to rest my belief on the evidence
which he brings forward here. I know no reason why one would not
be equally justified in explaining the synchronism in the division of the
several nuclei by assuming that all the masses of nuclear substance are
subject to the same laws and rate of growth, —that each requires the
same time in preparation for division. The synchronism of the events
is no more an argument in favor of an initiative activity on the part
of the protoplasm than on the part of the nuclear substance. There
may be no objection to saying that the protoplasm acts alike and
simultaneously on all the nuclei; but it might be said, with equal
justice, that all the nuclei, being chemically alike, act alike upon the
protoplasm, and, being of the same age, act simultaneously.
In his paper on the development of Heteropods, Fou (’76, pp. 112-
114) still maintains opinions already alluded to in connection with his
paper on Pteropods. Not only does the nucleus disappear at each
segmentation, but it becomes twice fused with the surrounding proto-
plasm, and as many times individualized, before the first segmentation
(p. 113). The nucleus which has reappeared in the central star disap-
pears again to give place to two centres of attraction, ete. ‘The
segmentation takes place in the well-known manner. Then the nuclei
reappear in the centres of attraction of the first two spherules, and the
same phenomena are reproduced at each of the subsequent segmenta-
tions.” (p. 114.) The nature of the spindle may be learned from the
account given of the maturation spindle. “The stoutest of these (aster)
rays are those which pass from one centre to the other in the interior
of the nucleus.” The fusiform body (Auerbach) he considers to be only
the central part of the disappeared nucleus; it is the body described in
Geryonia as the remnant of a nucleus. As to the fibres, they are only
striz in the protoplasm (p. 112).
In his “comparisons et reflexions,” the author treats these phe-
MUSEUM OF COMPARATIVE ZOOLOGY. 325
nomena with such freedom of interpretation that one is constantly
meeting with surprises. He has maintained, as above stated, that the
nucleus becomes fused with the surrounding protoplasm, but now claims
(p. 138) that its disappearance is not caused by a veritable dissolution
and mixing of its substance with this protoplasm, but that it is due
rather to a molecular change which renders it optically like the proto-
plasm, but without dispersion of its elements; and presently (p, 139),
when speaking of Biitschli’s opinions, he says: ‘‘ Je crois volontiers que
le nucléus se partage en deux et que cette division est visible chez les
vers.”
It appears to me another question whether, in its division, the nucleus
has an active ré/e. Certainly there is much to show that the activity is
not all on its part. As the author justly remarks, it cannot serve as the
centre of attraction presiding over the division of the cell, since the cen-
tres of attraction originate at the boundary of the nucleus and _ proto-
plasm. Although I cannot unreservedly subscribe to the belief that the
successive modifications of the nucleus take place in a manner “tout
a fait passive” for it, it is much easier to indorse the statement that
the nucleus deports itself in a manner quite as passive as the rest of
the cell.
Fol’s writings up to this time teach unequivocally that the new nuclei
arise at the centre of the radial structures of the protoplasm ; it is there-
fore surprising that the author now expresses his assent to Auerbach’s
discovery,* as though there were no fundamental difference between them
to be explained, and then calls attention to the grave error of Strasburger,
who mistook the protoplasmic mass (area) surrounding the centres of
attraction for the nuclei.
Biitschli’s spindle fibres are, in Fol’s opinion, filaments of sarcode ; the
granules (of the nuclear plates) are varicosities of the filaments, which
have no relation whatever with the nucleoli. t
Fol states, a little farther on, that the substance of the old nucleus
appears to contribute to the formation of the new nuclei.
Strossicu (76) has observed the radial arrangement of the protoplasm
* “Du reste, Auerbach a remarqué avec justesse que les deux taches claires qui
paraissent représenter le nucléus divisé et momentarément modifie, reparaissent dans
une position excentrique et se rapprochent ensuite du centre de chacune des deux
étoiles moléculaires.”
t The author seems to have made a slight mistake in stating (p. 141) that Biit-
schli’s first accurate description of the spindle and its fibres is to be found in his
communication in the July (1875) Heft of the Zeitschr. f. w. Zool. A very good
description will be found in the March number of that periodical, p. 208.
e
326 BULLETIN OF TIIE
in Serpula immediately preceding and accompanying segmentation. (See
p. 428.)
After alluding many times to the priority of his own discoveries in
this field of research, Fou (’76%) communicates important new consider-
ations resulting from his studies on Heteropods, the sea-urchin, and
Sagitta.
The centres of attraction appear before each segmentation at opposite
poles of the nucleus, which is still absolutely intact, and seem to be local
fusions of the substance of the nucleus [not quite “absolutely intact” 1]
with the vitelline protoplasm, or perhaps an bike of protoplasm into
the more fluid interior of the nucleus.
The difference in the appearance of the intranuclear (spindle fibres)
and the extranuclear filaments results from the former being immersed
in a medium almost liquid and much less refringent than the. protoplasm
of the filaments, while the latter are bathed in protoplasm, and for that
reason ought not to be so easily distinguishable. The difference between
these filaments is therefore only apparent and depends on the properties
of the substances surrounding them.
If the varicosities discovered by Biitschli appeared only upon the
intranuclear filaments, they would, in Fol’s opinion, establish a remark-
able difference between the two kinds. But that is not the case.
In the eggs of Geryonia and the sea-urchin varicosities are to be found
upon the extranuclear filaments, which have hitherto escaped all obsery-
ers. These enlargements are more elongated and less regular than those
of the interior of the nucleus, but they are, after all, indubitable vari-
cosities, which migrate like the others, and slowly become fused with the
central mass of protoplasm. This mass is, therefore, neither in its mode
of origin nor growth exclusively a derivative from the substance of the
old nucleus ; it is the result of a fusion of a part of this substance with
a part of the vitelline protoplasm.
As to the relation of these central masses to the new nuclei, the author
says he has often observed that, after having absorbed the greater part
of the radial filaments and their thickenings, they exhibit spots which
are clearer and probably more liquid than the rest of the mass, and which
have on this account been styled vacuoles. The new nucleus is the re-
sult of the fusion of these vacuoles. That which remains of the central
mass constitutes the envelope of the nucleus. Often, but not always, a
vacuole arises outside the central mass, on the side toward the old nu-
cleus. This shows that the liquid of the nucleus has the same double
origin as the masses themselves. The new nuclei result from a partial
MUSEUM OF COMPARATIVE ZOOLOGY. Son
liquefaction of these masses ; they are therefore composed of a mixture
—in very different proportions in different cases— of the substance of
the old nucleus and the protoplasm of the cell.
The observations made on Limax confirm much that is described by
Fol. Iam more inclined to think the asters result from a fusion of some
part of the nuclear contents with the vitelline protoplasm, and that it is
the chemical activity thus brought about which induces the radial ap-
pearance, than to assent to so crude an explanation as is implied by an
irruption of the protoplasm into the nucleus, however much the figure in
Fol’s paper on the Pteropods (Pl. VIII. Fig. 4) may resemble such an
invasion.
While I do not believe the whole difference between intra- and extra-
nuclear filaments can be ascribed to the media in which they are found,
— which, according to Fol himself, become optically the same ! (see above,
p. 325), — the occurrence of thickenings in the extranuclear filaments is
sufficient to suggest a closer relationship between them and the spindle
fibres than has been generally admitted. My own studies are not ade-
quate, I regret, to either confirm or refute the observation respecting the
migration of the extranuclear varicosities.
The part of Fol’s description which agrees least with my own observa-
tions is that which concerns the relation of the new nuclei to the central
masses (areas) of protoplasm.
The second paper by O. Hertwic (’77) on “ Bildung, Befruchtung und
Theilung,” etc. embraces studies on the eggs of two of the Hirndinea (He-
mopis and Nephelis), and of Rana temporaria and R. esculenta. Although
this paper does not undertake the discussion of cell division and the ac-
companying changes of the nucleus, it indirectly has much to do with
these phenomena, since the conclusion is here for the first time reached
and formally presented, that the production of the polar unas takes place
im the manner of cell division.
In a foot-note Hertwig (pp. 48, 49) says a few words about cell division
in frogs’ egys. Soon after the division of the segmentation nucleus, there
is found imbedded in the finely granular substance of each of the heads
of the dumb-bell figure a group of numerous large and small vesicles,
which are mutually flattened by reason of their closeness. These are
tinged in carmine, and possess the properties of small vacuolar nuclei.
They are produced from the separate granules of the condensation zone,
which simultaneously imbibe nuclear fluid. Each group therefore cor-
responds to a single daughter nucleus.
The division of the yolk appears to be effected by the contraction of
328 BULLETIN OF THE
its protoplasm, especially of the superficial layers. The pigment which
is located in the latter follows the depressions of the furrows. |
Of still more interest, since corroborating the observations made on
Limax, is the brief statement made (p. 24) concerning the appearance of
the spindle and the mutual relation of the conjugating pronuclei in the
case of Nephelis. Hertwig has never seen these two structures melt
together into a single nucleus, notwithstanding the examination of nu-
merous preparations ; not even in cocoons presenting at the same time
eggs with conjugated nuclei and others about to undergo the first seg-
mentation. He therefore concludes that this fusion stadium can probably
be of only short duration. Perhaps the fusion in the majority of cases
takes place only when the two flattened nuclei begin to elongate and
become metamorphosed into a spindle.
It seems to me probable that Nephelis is not unlike Limax in this
matter, and that the observer may in Nephelis look in vain for an elon-
gation of the pronuclei, since in reality a fusion of these structures is an
accomplished fact only when the nuclear spindle is formed. Hertwig’s
suggestion, that the fusion may take place synchronously with an elon-
gation of the pronuclei, does not rest, as I understand, on the observa-
tion of an elongated condition, but is inferred to exist from analogy with
cases where the two pronuclei fuse and the resultant segmentation
nucleus elongates. I would suggest that a still more radical difference
may obtain here, and that neither a distinct morphological segmentation
nucleus nor an elongation of the separate pronuclei finds expression in
the case of Nephelis.
Branpt’s (77) paper on segmentation in Ascaris aims at a reconcilia-
tion of the earlier observations of Biitschli (‘73*) and Auerbach (’74), by
calling especial attention to the amceboid nature of the germinative vesi-
cle, and of nuclei in general. It is possible (p. 374) that the eaxtenswe
and ramified pseudopodia of the germinative vesicle first segmentation
nucleus], which at the time of segmentation are vigorously amceboid,
exercise a strong stimulus upon the contractile yolk substance, and
thus favor segmentation.
The neglect to use reagents explains the fact that Brandt failed to
see anything of a spindle structure or its elements, and perhaps also
that the radial phenomena which he observed were only such as unfavor-
able objects have revealed to other observers. The new nuclear struc-
tures which Auerbach describes as vacuoles in the handle of the
dumb-bell are only an indication to Brandt, that the nuclear pseudo-
podia first to be retracted are those occupying the side of the cell next
MUSEUM OF COMPARATIVE ZOOLOGY. 329
the plane of segmentation. These, however, are not always the first
to be withdrawn. The “vacuoles” may result from a mechanical
stimulus inaugurated by the rupture of the nucleus. (!)
As segmentation advances, the cells become successively smaller, and
the nuclei, though absolutely smaller, are proportionately much larger
than at first. They grow at the expense of the yolk, which ultimately is
entirely consumed, — a confirmation of the theory that the germinative
vesicle is the primary egg cel/.
The influence of abnormal fecundation on the process of cell division
as given by Fou (’77°) will be found in the part of the present paper
devoted to fecundation.
McCrapy (’77) seeks the explanation of segmentation in the amoeboid
nature of his “protembryo” (p. 177), and is compelled to assume the
existence of an wnseen protoplasmic matrix to explain, for example, the
approach and mutual flattening of segmentation spheres after their
separation. He finds himself compelled to admit that O. Hertwig’s ob-
servations make it impossible to exclude a selective polar force, and he
proceeds to show how this polar force may be supposed to operate in
segmentation. Although apparently irreconcilable, McCrady thinks
the two theories (Hertwig’s and his own) may not be really incompatible.
Branvt (’77°) has communicated observations on the eggs of Lymneus
‘stagnalis and Anodonta anatina, in which the amceboid nature of the
germinative vesicle and of the nucleus is deemed sufficient to account for
the phenomena accompanying maturation and division.
In the case of Lymnzeus (pp. 591-593) the condition of the nucleus
during the first part of the first segmentation was not satisfactorily fol-
lowed, but during the stage of the mutual flattening of the segments the
nuclei were seen. At this time they appeared as clear structures of a
stellate shape, which were possessed of ramified, more or less radial pseu-
dopodia, and were constantly undergoing changes of form. It was owing
to the instability of their forms that they were at times very distinct
and sharply defined ; at other times less distinct, or even invisible.
After citing several authors whose observations are thought to be
capable of an interpretation substantiating the amceboid hypothesis, the
author says (p. 598): “Im Ganzen herrscht bei den citirten Autoren
die Ansicht vor, die strahlenformigen Figuren wiiren auf ein Structur-
verhiltniss des Dotters zu beziehen. Meine friiheren Beobachtungen
am Ascaridenei zwangen mich dieser Ansicht entgegenzutreten und die
Strahlen fiir Pseudopodien der Furchungskerne zu halten; zwischen
ihnen miissen eo ipso auch die Dotterkérnchen sich strahlenformig
330 : BULLETIN OF THE
lagern. Dieses Resultat bin ich nunmehr im Stande auf Limneus
auszudehnen, und so diirfte wohl der Nachweis ihnlicher Strahlen fir
die tibrigen Thiere einen Riickschluss auf die amédboide Beweglichkeit
der Furchungskerne gestatten.”
The close relationship between Limax and Lymnzeus allows me to speak
with more confidence than might otherwise be the case. It is to be
noticed that the phenomena which Brandt interprets as due to extensive
amoeboid movements of the nucleus, are thus explained on what seems
to be very insufficient evidence. The inference drawn from the fact,
that in place of distinct nuclei there are to be found only irregular and
often indistinct figures which undergo change of form and _ position, is
far from satisfactory. Further, proof is not produced that the irregular
amoeboid figures are nuclear structures. Nor is his position strength-
ened when it is subsequently maintained that the so-called nucleus is,
in reality, the cell; for enough is known of this so-called nucleus to
warrant the expectation that it will respond in a definite way to various
reagents. These, however, the author does not seem to have employed,
and it must be largely due to this fact, that his observations present
with undue prominence certain features of cell activity and entirely
ignore fundamental internal changes. If we both arrive at the same
negative conclusion respecting the complete dissolution and disappearance
of the germinative vesicle and its descendants (nuclei), it is nevertheless
from quite different data. The motion which results from the ame-
boid character of the nucleus is not competent to explain its admitted
absence (Brandt, 77°, p. 592 and Fig. 7), but on the contrary should
make the moving masses — the pseudopodia — more readily discernible.
Even without the evidence which other methods of research bring to
bear on this question, I should agree with Warneck (’50, p. 115), who has
observed similar phenomena and referred them to an unequal distribu-
tion of the elementary corpuscles of the yolk. If it be objected that
he makes no attempt to explain the cause of the unequal distribution of
these corpuscles, and that consequently he may not be cited as conflict-
ing with the ameboid theory, I reply that he does not anywhere admit —
such radical changes in the form of the nucleus as Brandt maintains, and
that some of his figures appear to me quite inexplicable under that theory.
I would especially call attention to his Tab. IV. Fig. 10” (compare with
the text at p. 125), where the inequalities in the distribution of the
corpuscles are as conspicuously represented as in any of his figures, and
where the nuclei (two pronuclei) are represented with the greatest distinct-
ness as sharply defined spherordal bodies.
’
|
]
|
|
|
MUSEUM OF COMPARATIVE ZOOLOGY. ok
Iam strengthened in my belief that the phenomena described by
Brandt are only more extensive exhibitions of what Warneck has de-
picted, by the fact that Brandt has himself cited the observations of the
same author, and even called attention to Figs. 3’-—5’ of the above-men-
tioned plate in confirmation of his theory.
Biscuorr ("77), to whom Embryology owes so much, has recently con-
tributed to the discussion of the questions under consideration, without,
however, bringing new material to the elucidation of the subject.
Two points of very general interest receive his attention :—(1.) The
unreliable methods of investigation, by means of hardening and stain-
ing reagents, etc., which have recently become so popular, are respon-
sible for misunderstandings and misconceptions which otherwise would
be avoidable. (2.) The greatest confusion as to the nature of the animal
cell has arisen through a confounding of its morphological with its physco-
logical nature. While all agree that the cell is physiologically an ele-
mentary organism, things the most diverse, from a morphologico-histologie
standpoint, are indiscriminately called cells. The same confusion is
responsible for the idea that the egg is a primary cell. ‘“‘ Meiner auf
Erfahrung, so weit sie reicht, gebauten Ansicht nach, ist nur das Keim-
blischen eine wahre primire und die einzige Zelle, von der bei dem nicht
in der Entwicklung begriffenen Ei die Rede sein kann, und das Ei selbst
wird am passendsten ganz allgemein als eine Umhiillungs-Bildung einer
Zelle aufgefasst. Ich glaube ferner, dass jedes rezfe Ei an seiner primd-
ren Bildungsstdtte im Hierstocke nur, aber auch immer, aus Keimblaschen,
Dotter und Dotterhaut besteht.” (p. 12.)
As regards the fate of the nucleus during segmentation, although
granting that the question has not reached a final elucidation, Bischoft
(p. 43) evidently inclines to the side of Auerbach and those who believe
in its dissolution at each act of division. Were Bischoff to write in the
light of what has been described within the past two years, it may fairly
be doubted if he would persist in saying that new nuclei are formed quite
independently of the old nucleus ;* there is already too much evidence,
independent of the supposed deceptive appearances produced by reagents,
to make this position longer tenable.
It seems incumbent on those who hold, with Bischoff, that the germi-
native vesicle is not a cell naclews, to explain why the vesicle undergoes
the same modifications previous to the formation of the polar globules
* “Bei der Einleitung zur ersten Theilung das Keimbliischen und sein Kern
schwinden, und ein neuer Kern sich wnabhdngig von diesen bildet. Was das erstemal
_ geschieht, wird auch wohl das zweite- und drittemal geschehen.” The original is not
Italicized.
332 BULLETIN OF THE
that the nuclei of embryonic cells and of segmentation spheres present
initiatory to the acts of division.
_ ‘Two communications from Garp ("76 and "77) are in so far of interest
here as they ascribe to Biitschli the idea that the polar globules arise in
the eggs of Lymnzus, Succinea, Nephelis, and Cucullanus by the pro-
cess of cell division; the author then says that he is able to add that
the same is the case with Salmacina Dysteri, and Spirorbis (77, p. 566).
I do not know how the author can ascribe this idea to Biitschli, for
the latter seems not to have yet arrived at that conclusion when the
first paper (Giard, "76) was published, and gave no expression to such a
notion until some time after Giard’s second paper had appeared.
P. Mayer (77, pp. 212, 213, Taf. XIII., XIV.) says that no nucleus
is to be found, even with the use of the ordinary reagents, in freshly
laid eggs of Pagurus Prideauxii, but in the course of a few hours one be-
comes visible. Subsequently the single nucleus has given place to two,
then to four, and finally to eight. It is only after the formation of eight
nuclei that the segmentation begins, nor are there eight cells formed at
once, but first two, then four, then eight. Mayer did not, on account of
the opacity of the eggs, observe the division of the nuclei. It is not
possible to say from his figures whether the nuclei undergo a spindle
metamorphsis, though the same is to be inferred, since he refers to the
presence of Auerbach’s karyolytic figure as a matter that scarcely needs
to be stated. In his opinion, however, the nucleus is not dissolved, but
is directly divided. He has seen long-drawn nuclei and even two nuclei
in a cell about to divide, without thinking it necessary to conclude that
they are pathological conditions.
StossicH (77) gives an account of the nucleus during division, which
will be noticed elsewhere (p. 448).
Burscuut (77°, p. 236) states that he has, at the same time with, and
independently of Giard, arrived at the same conclusion touching the cell
nature of the polar globules, though he lays no claim to having expressed
that opinion in the works which were accessible to Giard when he wrote.
“Giard hat sich auf Grund meiner friiheren Beobachtungen diese Ansicht
gebildet.”
This paper of Biitschli contains no further contribution to the nature
of cell division and nuclear changes, save the exception which is taken
(p. 240) to Robin’s view, —that smaller segments arise from larger ones
in the case of Nephelis by a budding process, in which the nucleus takes
no part. Robin’s position is sufficiently refuted by Biitschli’s figures
and remarks.
|
|
|
|
|
MUSEUM OF COMPARATIVE ZOOLOGY. 333
HoFrMann (77) was unable to follow any of the internal changes ac-
companying the segmentation of eggs of Malacobdella (p. 23), but found
that a constant change of the external form of the yolk accompanies the
earlier segmentations. In Clepsine the same author (’77“) has by means
of sections been able to see something of the stellate figures (of which
his Fig. 10 gives a rather diagrammatic view), but nothing of a spindle
figure during segmentation (p. 35).
SELENKA (78) has given a preliminary account of observations on liv-
ing eggs of Toxopneustes variegatus.
During the union of the sperm- with the egg-nucleus to form the pri-
mary cleavage nucleus, the plasma, which constituted the central area of
the radial figure surrounding the former, in part flows around the egg.
nucleus, and thus gives rise fo a second central area. These two central
areas diverge, the cleavage nucleus becomes ellipsoidal and suffers a
metamorphosis, while the yolk becomes flattened in the direction of the
axis of the nucleus. The latter exhibits at each pole one, and then sev-
eral deep incisions, resulting in a longitudinal fission of its whole sub-
stance into some twelve cylinders (Kerncylinder). An equatorial nuclear
plate arises and splits into two plates, each composed of twelve “ Kern-
stabchen,” or ‘ Vorkerne,” arranged in a circle. These migrate to the
respective ends of the nucleus, which has meantime become an elongated
eylinder, and here they melt together, first into six, then into two, and
finally, but slowly, into a single new nucleus, which rapidly grows to
, double the size it had at first. A constant increase in the mass of the
|
“Vorkerne” accompanies their union, and is caused by the absorption of
the contents of the “ Kerncylinder,” which is really composed of pro-
cesses of the “ Vorkerne.” The flattening of the yolk is followed by a
lengthening in the same axis, and finally it assumes the constricted form.
The first constriction may, however, disappear before it has accomplished
the separation of the halves, to reappear only when two more nuclei
have been formed and a second constriction has made its appearance, in
a plane perpendicular to that of the first. Selenka considers this, as
well as the usual method, normal, and is inclined to seek an explanation
of the former in the hastened division of the primary cleavage nu-
cleus.
AvERBACH ("77) has given, in a paper which I have not been able to
secure,* an explanation of the striation of the spindle. It does not neces-
_ Sarily originate in the same manner in all cases. If the granules imbed-
* This account is taken from Hofmann u. Schwalbe’s Jahresbericht, Bd. VI.,
Anat. Abth., p. 25.
334 BULLETIN OF THE
ded in the viscid substance of tue nucleus are themselves viscid, they
will be drawn out into filaments with thickenings at one end or in the ~
middle according as the traction is from one or both sides. Thus it
happens in the division of the sperm mother-cells of Strongylus auricu-
laris that the nucleoli, arranged in rows, are converted by this stretching
into meridional fibres; but if the numerous spherules are movably im-
bedded in the viscid matrix, then an elongation of the latter will cause
the former to arrange themselves in parallel rows, which will give origin
to a striate appearance.
GROBBEN (’78, p. 38, Taf. III. Fig. 17) has often seen the spindle-
shaped nucleus with fibres and prominent equatorial thickenings in the
large testis cells of Astacus.
In his paper on the organization and development of the Oxyuride,
GaLeB (’78*) has given an account of the nucleus during segmentation,
In Oxyuris blatticola (p. 365) one finds eggs in the following conditions :
non-segmented eggs with a germinative vesicle [primary segmentation
nucleus ?] near one of the poles (Pl. XXII. Fig. 1) ; others with the germi-
native vesicle elongated into the shape of a biscuit and in process of
division (Pl. XXII. Fig. 2). Subsequently the germinative vesicle di-
vides, and one then sees two vaguely rounded clear spots in the vitellus.
The figure cited (Pl. XXII. Fig. 3) represents each of the spots as
embracing a single nucleolus. The segmentation follows rapidly, and the
halves of the ‘‘ germinative vesicle” separate, the larger portion migrating
to the opposite pole of the egg. The inequality in the size of the first
two segmentation spheres may be attributed (p. 366) to this inequality ©
in the size of the segments of the germinative vesicle ; each portion of
the latter probably exercising an attractive force upon the vitelline
granules proportional to its volume. Although the author has seen the
stellate figures in the eggs of other animals, he has never succeeded in
doing so here, and concludes that they are concealed by transparent
fatty vesicles, unless, however, their production is caused by the em-
ployment of reagents. In fact something of this radial structure was
seen after using reagents in the case of O. Kiinckeli. Of a spindle
metamorphosis of the nucleus, the author may be said to have seen
nothing.
In the last chapter of his book, “Ueber das Ei,” etc., Branpr (78)
argues further to show that the supposed disappearance of the ger-
minative vesicle (and of the nucleus during segmentation) is due to
the active amoeboid changes of its form. “Die Theilung des Keim-
blischens, sowie die der Furchungskerne, vollzieht sich unter wech-
MUSEUM OF COMPARATIVE ZOOLOGY. 335
selnden amceboiden Gestaltabweichungen (Strahlensonnen von Pseudo-
podien).” (p. 177.)
The inaccuracy of his conceptions of the nature of the ‘Strahlen-
sonnen ” is too apparent to need a special refutation. To consider these
astral figures, which belong primarily to the protoplasm of the yolk, as
pseudopodia of the nucleus, is to ignore the evidence of most careful
observers ; to claim that the nucleus is capable of automatic change of
form, is quite another thing, to which I cannot object. How far Brandt
is misled by the observations of others appears (p. 178) from the view
held by him that the membrane of the germinative vesicle becomes the
spindle of Biitschli, while its active substance escapes from the membra-
nous enclosure at two opposite points. (!) The unreliableness of Brandt’s
conclusion, that the nuclear reteculwm is only a pseudopodal extension of
the nucleolus, and that the granules occurring in it are only local thick-
enings of the pseudopodia, has, I believe, been shown by the recent
exquisite researches of Flemming and others.
Repracuorr (’78) gives rather unsatisfactory figures of the condi-
tion of the nucleus during cell division. Before each segmentation
it becomes homogeneous, and the beginning of its division antedates
that of the cell. In Figs. 10-12 the author reproduces the stages
of nuclear division, showing the ‘‘dumb-bell” with a slender handle.
More or less prominent asters, centring in the homogeneously stained
heads of the dumb-bell, are figured. The heads are designated as
“Theilstiicke des Furchungskernes.” Neither spindle fibres nor thick-
enings seem to have been observed, nor yet the incipient stages of
nuclear formation, if, as is reasonable to suppose, this takes place in
the manner now known to prevail with the eggs of most animals.
The fourth chapter of the summary on fecundation, segmentation,
etc., given by Von JueRinG ('78,, pp. 143-156), is devoted to the
| phenomena of segmentation and cell-division. It does not lie within
| the aim of his paper to contribute new material to the discussion.
Besides the method of cell increase which Auerbach denominates
| palingenetic, and which may safely be said to be the most wide spread of
all forms, Von Jhering recognizes as different from it the free cell-forma-
) tion of the botanists, and the equivalent methods in the segmentation
_ of insect eggs and in the division of epithelial cells. As claimed by
| Strasburger, this latter method may be related to the former, in the
} Sense that it is produced by a shortening of the process of development.
| A simple genuine division (i. e. without metamorphosis of the nucleus),
| from which budding is in no way fundamentally different, cannot be
|
\
336 BULLETIN OF THE
denied, and appears to be realized especially in the case of unicellular
Protozoa. Finally, the endogenous method of cell increase, though much
less general than was formerly maintained, is not for that reason to be
totally denied. It occurs more especially in the Protozoa and the
Mesozoa (Dicyemidze). Cormmon to all forms of increase, save free cell-
formation, is a continuity in the successive generations of nuclei. As
Von Jhering’s review of the palingenetic method of cell increase is simply
a fair presentation of what appeared the more salient and unmooted
features of the process, with possibly a slight tendency to magnify the
observations of Selenka, I shall spare myself the trouble of reviewing his
statements in detail. In so far as his paper is a reflection of the ideas
prevailing at that time, it warrants me in calling attention to some
points at variance with observations on Limax. Von Jhering appears to
maintain a direct genetic connection between the radial figure of the
spermatic nucleus and one of the two stars which constitute the amphi-
aster of the first segmentation sphere.* Although assenting that the
asters are not always of the same age, I cannot agree, for reasons else-
where expressed, that there is any basis for assuming the implied con-
nection. The idea that the systems of yolk rays arise about the ends
of the spindle, rather than that the spindle is a differentiation which
may make its appearance somewhat later than the asters, is a one-sided
view of the possible order of events. It cannot be doubted that the
spindle fibres may far exceed the numbers (12-24) given by Von
Jhering. It is perhaps premature to say that “the Zellplatte in the
case of animal cells is of only theoretical interest”; at least, traces of
the structure in question are so persistent in Limax as to compel the
belief that not all of the substance of the interzonal filaments finds its
way into the new nuclei.
In his “ Zoologische Studien,” SeLenKA (78, pp. 11-14) extends and
somewhat modifies his preliminary communication. The incisions at
the pole of the segmentation nucleus, at first thought to initiate its
fibrous differentiation, are only phenomena of contraction in its welded,
but not yet intimately fused parts [pronuclei, Van Beneden], and they
* “Ten auf den Eikern zuwandernden Spermakern hatten wir als das Centrum fur
eine weitgehende Dotterstrahlung kennen gelernt, wahrend dem Eikerne, nachdem
er einmal seinen Platz im Centrum des Eies eingenommen, eine solche nicht mehr
zukam. An dem Furchungskerne, kurz nach seiner Entstehung, gewahrt man daher
nur ein Centrum der radiiren Dotterstrahlung. Sobald nun der Furchungskern
die Spindelform angenommen, erscheint noch eine zweite Sonnenfigur im Dotter,
indem jeder Pol der Spindel zum Mittelpunkte eines Strahlensystemes wird.”
(p. 150.)
MUSEUM OF COMPARATIVE ZOOLOGY. oot
disappear as soon as the nucleus has taken on the genuine spindle
shape.
Selenka believes he can add to the results reached by Auerbach, Stras-
burger, and Biitschli. Soon after the segmentation nucleus has taken
an elliptical form, its substance is separated into a protoplasmic nuclear
spindle, and a nuclear fluid surrounding it. The latter is so difficult to
distinguish on account of the “‘clear area” which surrounds the nucleus,
that it is easily overlooked, and hence arises the erroneous idea that the
spindle represents the whole of the contents of the nucleus shrivelled.
The nuclear fluid increases rapidly in amount, assumes a spherical form,
and finally ruptures the nuclear membrane (already figured by Biitschli),
and thus becomes mingled with the surrounding yolk.
During the fission of the nuclear plate a small lustrous corpuscle lies
at the tip of each end of the spindle. Whence it comes, Selenka cannot
say, nor can he add anything concerning the origin of the spindle fibres
or their thickenings ; but the segmentation nuclei of the second genera-
tion arise substantially from a fusion of the elements of the nuclear
plate, without the participation of any other formed structure.
From this it may be inferred that the corpuscles at the tip of the
spindle do not enter (at least without first suffering dissolution) into the
composition of the new nuclei. I fail to see, however, that the observa-
tions, so far as the figures allow one to judge (Taf. III. Figs. 18 —20), are
competent to prove this exclusion. If the exclusion of these corpuscles
were established, and if they are identical with the corpuscles occupying
the centre of the polar areas in Limax, (an identity which I do not feel
to be fully justified in view of their prominently eccentric position in the
terminal suns,) then I should find in Selenka’s statement a confirmation
of the opinion I have elsewhere ventured, viz. that the areal corpuscles
do not directly share in the formation of the new nuclei.
The nuclear fibres (14 — 24 in number) are at first separated from each
other by equal intervals; but when the fibre thickenings have advanced
to near the ends of the spindle, and have fused in pairs, these secondary
thickenings take the form of a circle [ring ?] and further unite, as has been
stated in the review of the preliminary paper. Instead of Vorkerne
used in the earlier communication, Selenka suggests the use of Mucleo-
plasts for the “ Kernfaserelemente,” since the former name (pronuclei)
is otherwise employed. When the “nucleoplasts” are six in number at
each pole, they have the form of conical rods with the tips directed out-
ward, their blunt ends united to the interzonal filaments.
After the formation of the segmentation nuclei of the second genera-
VOL. VI.— No. 12. 22
338 BULLETIN OF THE
tion, the radial figures disappear very rapidly, but the clear area in
which each nucleus is imbedded persists.
The primary cleavage nucleus in Clepsine is found to lie, according to
Wurman ('78*),* “a little eccentrically toward the oral pole. The
nucleoplasm is more strongly colored in the centre around the pronu-
cleolar bodies than at the edges.” There are usually three of these
“pronucleolar” bodies, which are “sharply outlined, but only slightly
stained with carmine.” “The longer axis of the nucleus in this stage is
in every instance at right angles to the axis of the egg, whereas, at the
moment of union of the pronuclei, the longer axis was found parallel to
that of the egg, and a little later inclined about 45°.” The “ pronu-
cleoli” are several times larger than when the pronuclei meet. Between
the nucleus and the oral “polar ring” a line, more highly colored than
the rest of the yolk, is sometimes seen. This, from its position and di-
rection, Whitman interprets as the path taken by the female pronucleus
toward the male pronucleus. It occurs to me that it may be the same
structure which Fol has seen in the Pteropod egg.
The nucleus elongates and then passes from a spindle- to the biscuit-
form. The “nucleoli,” having dissolved, are no longer visible, but there
stretch through the centre of the biscuit-shaped figure “‘fine granular
lines, which together form a sort of spindle, the poles of which appear to
be near the centres of the polar areas.” These interstellate lines are
more strongly expressed than the radial lines of the two polar areas.f
At this time, says the author, the substance of the “ polar rings” —
for an account of which the reader must be referred to the interesting
description given in the original paper — begins to plunge into the yolk,
and possibly contributes some elements to the nucleus which may stim-
ulate the molecular changes which result in the formation of the cleavage
amphiaster.
Subsequently, there arises in each pole of the amphiaster “a central
area t which colors less with carmine than the surrounding nucleoplasm,
and in the edge of which the converging rays end.” ‘These central areas
undergo a modification from the round to the biconvex, and finally to
* Compare also Whitman ’78.
+ The eggs of Clepsine appear to be very unfavorable for the study of the nuclear
plate, for Whitman was unable to find any trace of it during the first segmentation.
t This central area in a more advanced stage the author identifies with the cell
nucleus. His ‘‘nucleoli,” therefore, correspond with what many observers consider
the still unfused elements of a nucleus, and his “ nucleus” with what I have called
‘‘area.”’ A discussion of his views on this point will be found under Fecundation
(pp: 504 et seq.).
MUSEUM OF COMPARATIVE ZOOLOGY. 339
the meniscus form, during which changes they move in opposite di-
rections, as if repelling each other. The spindle fibres gradually
disappear.
At the completion of cleavage a cluster of four to six refractive “ nu-
cleoli” is formed in each of the areas, and the latter at that time begin
to approach, again passing through the same series of forms, but in the
reverse order.
Although not’ directly stated, it is to be inferred that these nucleoli
do not fuse until the formation of the second segmentation spindle.
In the fourth instalment of his “‘ Beitrage,” etc., O. Hertwie (787)
has devoted some attention to the phenomena accompanying the first
segmentation.
Living eggs of Mitrocoma seem to become enuclear by the sudden
disappearance of the mutually flattened pronuclei, but the use of acetic
acid establishes the presence of a fibrous spindle which is eccentric in
position and is accompanied by radial arrangements of the yolk at its
tips. The division begins, about two hours after fertilization, with a
furrow which makes its appearance at a point of the surface directly over
the spindle, and is accompanied by the formation of secondary smaller
folds in the cortical substance at right angles to the segmentation fur-
row. A number of small vacuoles — the metamorphosed halves of the
nuclear spindle — make their appearance in each segment when the fur-
row has advanced as far as the middle of the yolk, The portions of the
yolk last separated are those lying diametrically opposite the side occu-
pied by the spindle (p. 183).
The observations on Tiedemannia (p. 205) are more interesting since
the origin of the amphiaster is more successfully traced. The pronuclei
remain a long time close to the surface in an unaltered condition. At
length their nucleoli become disintegrated into clusters of smaller gran-
ules, which collect themselves on either side of the conjugating surfaces
of the pronuclei (Taf. XI. Fig. 5). Then two systems of faint rays make
their appearance at opposite edges of the surface of contact. Suddenly
the contours of the nuclei become indistinct, and both the vacuolar
spaces suddenly disappear, probably through a mingling of the surround-
ing protoplasm with the nuclear fluid. In the homogeneous protoplasm
one may still barely recognize the two systems of rays at some distance
from each other. The division follows much as in the medusa alluded
to above.
Although the contour is figured somewhat less boldly where the two
nuclei are in apposition, it is not stated that the nuclei actually unite
340 BULLETIN OF THE
before the disappearance of the whole outline, and I am inclined to think
this case is closely related with the condition found in corresponding
stages in Limax, where the evidence strongly favors the view that there
is not an actual union of the pronuclei preceding the appearance of the
asters. It is noticeable that Hertwig makes no mention of the spindle
in this case, doubtless from its tardy appearance, as in Limax. He does
not seem to have discovered the asters at any point other than those
which lie in the plane of nuclear contact, nor that they may come into
view successively. In both particulars the eggs of Limax have proved
more favorable in determining, if not the prevailing, yet at least the
possible, order of the events of nuclear metamorphosis.
In each of the conjugated nuclei arises in Pterotrachea a single, or in
Phyllirhoe numerous nucleoli, which are, however, of only temporary
duration. After their disappearance two radial figures arise, as in
Tiedemannia, but in the present case the partition between the two
nuclei disappears, so that an actual fusion takes place. In the nuclear
space thus made common, fine fibres stretch between the two suns.
Later, the contents of this nuclear vacuole, which in Hertwig’s opinion
contains in addition to the spindle nothing but nuclear sap, become min-
gled with the surrounding protoplasm, whereby the comparatively small
spindle comes to lie free in the yolk (pp. 208, 209).
In Pterotrachea, as well as in Mytilus, the activity of the vegetative
pole of the egg just before or during the first segmentation results in
more or less conspicuous protoplasmic elevations of the yolk. |
Very recently BoprerzKy ("78") has published observations on early
stages in the development of insects. He maintains that the blasto-
derm cells in certain Lepidoptera are formed within the yolk by a pro-
cess of cell division, and migrate as amceboid cells— hitherto mistaken
for nuclei—to the surface, where they successively make their appear-
ance to form the blastoderm.
Lana’s (78) studies on the development of Balanus contain indica-
tions that in the segmentation the nucleus undergoes a spindle meta-
morphosis, but give no data concerning the maturation or fecundation,
save that a segregation of the ectodermal protoplasm at one pole pre-
cedes the “ unequal segmentation.”
Hatscuexk ("78) has given little attention in his excellent paper on the
development of Annelids to the details of cell division. He says, how-
ever, (p. 17,) that one very often finds in the primitive cells of the meso-
derm indications of division, — spindle-shaped nuclei, and granular rays
in the protoplasm.
|
|
|
|
9
MUSEUM OF COMPARATIVE ZOOLOGY. 341
B. Tissues. — Observations upon metamorphosed nuclei of tessue cells,
certainly referable to a process of division, are mostly of quite recent
date, and the papers which treat of them are largely the result of the
‘stimulus afforded by discoveries in connection with segmentation.
The papers of Biitschli and Strasburger in 1875 served to recall the
attention of Mayzeu ("75)* to certain appearances of nuclei which he
had often observed in his studies on the regeneration of epithelium, and
which up to this time had remained problematic to him. In essential
agreement with the observers alluded to, he at once came to the conclusion
that the existence of numerous coarse granules and fibrous structures
in the nuclei was connected with the process of nuclear division.
The cornea of the rabbit and the cat, but more particularly the
cornea and other epidermal structures of the frog, were the objects
studied. Mayzel was unable to confirm by studies on fresh specimens
the results attained in the use of different reagents. Although occa-
sionally observed in regions of normally preserved epithelium, the
appearances were most frequently met with in the tracts where regen-
eration had followed an artificial removal of the epithelium, and then
not at the edge, but in the midst, of the regenerated portion, and in the
deep rather than in the superficial layers. He distinguished three
principal forms of the nucleus, without, however, being able to affirm
positively that they follow one another in the order in which they are
described : —
(1.) Large oval nuclei of twice the diameter possessed by their
neighbors, either coarsely granular at the periphery only, —thus dis-
closing the nucleoli, — or throughout ; then such as have their granules
elongated into threads, and knotted together; and finally those with
similar filaments, alike in thickness but of various lengths, arranged
radially about a central point.
(2.) Large, elongated, spindle-shaped nuclei, with a thick transverse
disk which appeared either more nearly homogeneous, or else as if com-
posed of coarse, refringent granules of unequal size. Occasionally the
disk appeared double. The remnant of the indefinitely outlined nucleus
was delicately fibrous in the direction of the long axis, the fibres so
- converging at the ends of the nucleus as to give it the appearance of two
_ fibrous cones placed base to base.
* As I learn from Flemming (75, p. 186) and Strasburger ('76, p. 230), KLEBs
(74) had already noticed early in 1874, in studying the regeneration of epithelium,
aradiate arrangement of the protoplasm which he connected, however, with the genesis
_ of new, rather than with the division of previously existing, nuclei.
942 BULLETIN OF THE
(3.) Nuclei of like size, but more elongated, the two ends consisting
of two saucer-shaped structures with their cavities facing, and the inter-
vening portion occupied by numerous filaments differing in thickness
stretched between these two structures. The “saucers” appeared at
times as though composed of radiating filaments, at others as though
made up of a nearly homogeneous, lustrous substance. The equatorial
disk is no longer visible. The distance between the saucers is now
more, now less. The connecting fibres rupture successively. The
‘saucers ” become flattened into disks, and appear either as a mosaic of
rods or else homogeneous. The disks become thicker and rounded, and
acquire vacuolar cavities in which nucleoli appear. They now nearly
resemble the neighboring nuclei. |
Accompanying changes in the shape of the cell and its constriction
ultimately end in cell-division, the nuclei, at first close to each other,
sometimes appearing to be still joined by fine filaments. They subse-
quently move apart, and the cells, like those which surround them,
become polygonal.
Mayzel ventures the statement that, at the free edge of the regenerat-
ing patch of epithelium, the nuclei are without doubt formed [not by
division but] by differentiation out of the protoplasm.*
The observations of Ed. van Beneden (75) on ectoderm cells of the
rabbit embryo are to be found at pp. 302, 303.
SEMPER (75°, pp. 361, 362, Taf. XIX. Fig. 29, x), among the “ Ureier”
of Acanthus, found some whose nuclei were smaller than usual and ap-
peared to be composed of small granules often radially arranged about
a centre. Such nuclei are more deeply stained in hematoxylin than
the ordinary nuclei. Semper is inclined to connect them with the pro-
cess of cell division, especially in view of their close similarity to the
phenomena accompanying segmentation, as shown by Biitschli, Auer-
bach, and Flemming.
EwetskyY ("75) seems, according to Strasburger (76, p. 228), to have
figured something of the phenomena of nuclear division. I have not
been able to consult his paper.
Besides his study of the blastoderm cells of insects, the results of
which have already been given (p. 320), Butscuir (76, pp. 249 — 262)
extended his investigations to an examination of cell and nuclear
division in the germ cells of the spermatozoa of Blatta, and in the
blood-corpuscles of the fowl, the frog, and Triton. The more important
* “Tass die Kerne ohne Zweifel durch Differenzirung aus dem Protoplasma sich
frei bilden.”
MUSEUM OF COMPARATIVE ZOOLOGY. 343
results, as far as regards Blatta, have been given in connection with the
review of his preliminary article (p. 289), and I will here call attention
to only one or two points dwelt upon in this ultimate paper.
The nuclei of the “great germ cells” exhibit, after the employment
of acetic acid, numerous dark granulations which are united to each
other by fibres, — strung on the latter, as it were. These fibres may
constitute an irregular net work, running through the whole nucleus, or
they may take a quite regular, bush-like form. In the latter case they
arise from a point of the nuclear membrane about which granules of the
cell protoplasm are grouped. In clusters of neighboring nuclei these
points are turned toward each other, a fact which leads to the conviction
that a process of nuclear multiplication takes place with these “ great ”
cells. This opinion is strengthened by finding two such nuclei still
connected by fibres. After these “‘great” cells had become isolated
from each other, the nuclear metamorphosis was followed in the liwng
cells, as far, at least, as to establish a fibrous nature for the elongated
oval nucleus. Occasionally an equatorial thickening was also visible.
There is little to be seen in his figures of a central area, though the
radial structure is well shown in some cases. (See Taf. V. Figs. 14, 17,
op. cit.) .
The daughter nuclei arise by a differentiation out of the dark homo-
geneous nuclear plates (Kernplattenkorper). This differentiation is to
be considered as most probably brought about by the accumulation of
fluid between an exterrial layer (nuclear envelope) of this dark, homo-
geneous body and its central portion (nucleolus). This originally single
nucleolus suffers a disintegration into a number of parts, each still con-
nected with interzonal filaments. Nothing like a cell plate is to be seen.
The very interesting statement is made that sometimes masses of
protoplasm containing ¢wo nuclei undergo division. This was observed
to take place in one or the other of two ways. In both methods the
two nuclei divide at the same time and give rise to two spindles having
parallel axes; in one case the protoplasm is grouped about the two
daughter nuclei, which occupy corresponding ends of their respective
Spindles, as if about a common centre ; in this case two binuclear cells
result ; in the other case the components of one set of daughter nuclei
| may separate from each other and become the centres of two smaller
| cells. In the latter case the result is one binuclear and two uninuclear
| cells.
a ,
| Biitschli draws the conclusion that a common cause, resident only in
the surrounding protoplasm, affects the division in these cases.
t
344 BULLETIN OF THE
The blood-corpuscles of the embryo fowl, on the fourth or fifth day of
incubation, when treated with reagents, furnish satisfactory proof that a
nuclear metamorphosis accompanies cell division. ~The so-called equa-
torial plate may in this case be composed of distinct rods, or may be an
actually continuous plate as in many plants. The spindle as a whole
is so large as to lead to the belief in an zncrease in the volume of the
original nucleus. Faint traces of a second equatorial thickening are
found and interpreted as a cell plate.
Regarding the structure of the nuclei of blood-corpuscles Biitschli is
(p. 260) at variance with Auerbach (’74, pp. 61—70, 98, 103, 114) inas-
much as he finds that the nuclear substance exists in the form of irregu-
lar fibres, with nodose thickenings in many places, which traverse the
nucleus and are united with its envelope, rather than as discrete nucleoli.
The division of the white blood-corpuscles in Rana and Triton is accom-
panied by changes of the nucleus which present only a remote re-
semblance to the typical metamorphosis of this structure. There is
simply an elongation of the nucleus, and a gradual swelling of its ends;
while the middle, connecting portion becomes attenuated to a fine
thread, which probably ruptures and becomes incorporated in the two
daughter nuclei.
STRASBURGER’S (76, pp. 208-211) observations on nuclear division in
animal tissues were limited to studies on fibrous cartilage from the ear
of the calf. Notwithstanding the unfavorable nature of the object, —
preparations from which leave much room for the play of the imagina-
tion, — Strasburger believes the division takes place by the lengthening
of the nucleus, and the formation of an equatorial plate whose halves
separate and leave stretched between them “nuclear filaments,” before
there is any sign of a division of the protoplasm. In the equator of the
nuclear [interzonal] filaments, and in the surrounding substance as far
as the wall of the cell, there is then seen a dividing layer, —the begin-
ning of the cell plate. This partition is not formed progressively from
the circumference inward, but is produced simultaneously throughout
its whole extent, and subsequently splits, as in plant-cells, into three
layers, of which the central forms the fibrous intercellular substance of
the cartilage.
Studies by Eserru (’76), immediately induced by Strasburger’s work,
and carried on without a knowledge of what Mayzel had done, corrobo-
rate most of the conclusions of the latter author. On the cornea of the
rabbit and the frog Eberth has also shown that after artificial removal
or destruction of the epithelium the ensuing regeneration affords oppor
Siam en a a a
—_ z ——s
he Fae
On A A SA RE
MUSEUM OF COMPARATIVE ZOOLOGY. 040
tunity to study nuclear division, and usually at some distance from the
injured spot. Also on preparations of the normal cornea made with
gold chloride, certain nuclei appear larger than the others, and are
composed of clusters of lustrous corpuscles, somewhat smaller than the
smallest nucleoli. In addition there are found simply curved and
S-shaped lustrous rods of the same diameter as the granules, with
knoblike ends. These are often radially arranged.
In the rabbit’s cornea undergoing regeneration occur similar phe-
nomena. When the granules are not too close together one sees be-
tween them the larger nucleoli. Moreover, only a part of these granules
are free like the nucleoli; others appear as small thickenings in the net-
like system of filaments which form the nuclear stroma. In other cells
the nuclear membrane and the nucleoli are no longer to be found, and
in place of a granular nuclear substance there is an irregular, lustrous,
starlike structure, half as large as the nucleus previously was. The rays
of this star are either plump, or, if slender, have terminal swellings, and
may be elongated and spindle-shaped. A clear area, surrounding this
figure, more or less sharply defined from the surrounding protoplasm, is
the remnant of the previous nucleus. The fibrous mass becomes short-
ened and thickened, and thus assumes the shape of a double convex lens,
or a sphere, of meridionally arranged rods and granules. An equatorial
fission separates this structure into hollow hemispheres, — each a sort of
fibrous basket. The granules have now become less abundant, having
probably been converted by fusion and elongation into filaments; at
least the latter are more numerous than previously. The parting -fila-
ments are often swollen, at other times they end in attenuated ex-
tremities. They vary in length, and may anastomose with each other.
The separation is not effected at the same instant in all the fibres, a
part retaining their connection for some time. The basket structures
Separate, and after the parting of the last delicate traces of the equa-
torial ends of the fibres their peripheral ends terminate in a cluster of
lustrous granules, or a crescent-shaped body, and are no longer distin-
guishable from each other. The crescent-shaped body grows at the
expense of the fibres, and there results in place of the fibrous basket an
oval, jagged body — the new nucleus — surrounded with a clear area.
This new nucleus is a sort of shallow cup of homogeneous substance.
The clear area is the result of the constriction and division of the area
which previously surrounded the two fibrous baskets. The cell undergoes
division during the conversion of the basket into a homogeneous, jagged
body. The latter subsequently changes into a larger vesicular nucleus.
|
346 BULLETIN OF THE
In spindle-shaped cells of the cornea (rabbit) a fine line which traverses
transversely the space between the two incipient nuclei (op. cit., Taf. XX,
Fig. 1. d) is thought to be an indication of the coming cell division. It
may, then, I would add, correspond to Strasburger’s cell-plate. Similar
changes accompany the division of other cells, and are very conspicuous
in the frog’s cornea. In the Descemet’s cells of the latter the fibrous
mass is sometimes divided at once so as to give rise to four new nuclei,
perhaps in some cases to six or seven.
The conclusions drawn by Eberth are, to epitomize: — Many cells do
not divide simply, but first undergo a metamorphosis which begins with
an enlarging of the cell and its nucleus. The latter, by absorption of
fluid from the cell protoplasm and by differentiation into clear fluid
(Saft), lustrous granules and filaments, becomes lighter. The granules
are not derived from the nucleoli, however much they resemble them,
for the two coexist. The nuclear membrane is dissolved, but neverthe-
less a mingling of the nuclear matter with the protoplasm does not take
place. Since the granules and filaments often appear before the dis-
solution of the membrane, a complete karyolysis (Auerbach) does not
take place. The fibres and granules form a jagged, or globular body,
or a spindle figure, whereupon the fibres usually take a regular meridional
course, but may remain quite irregular. In the latter case a more
regular arrangement is only apparent after the beginning of the divis-
ion, which takes place as above described. The fibrous mass, which has
arisen in the mother nucleus, is the new nucleus, and gives rise by
division to two (or sometimes four or more) daughter nuclei. The
mother nucleus, in some cases at any rate, is still present in the later
stages of metamorphosis, and is converted into the substance of the
daughter nuclei.
The principal points of difference in the changes of corneal cells as
compared with plant cells (Strasburger) are :— The differentiation does
not (cornea) begin with longitudinal streakings, but at once with
the appearance of the equatorial granules and filaments, which furnish,
if not always the whole, certainly a great part of the material for the
new nuclei. In the young, cup-shaped, homogeneous nucleus reappears
later a differentiation into clear fluid and anastomosing filaments, which
latter then undergo a granular disintegration or are changed into a net
of fine “‘ Bailkchen” and thus form the stroma of anew nucleus. There-
by the nucleus appears granular. It then increases in size at the
expense of the substance of the old nucleus, whose fluid is probably
absorbed by the young reticular nucleus. In the corneal epithelium of
9
MUSEUM OF COMPARATIVE ZOOLOGY. B47
the frog, however, the greatest part of the substance of the old nucleus
seems to be employed in forming the filaments, and the little that is left
appears to be mingled with the surrounding protoplasm ; for, before the
division of the new nucleus into the daughter nuclei, the clear remnant
of the old nucleus has disappeared.
Basrani (76) has studied the nuclear changes during cell division
in the epithelial cells of the ovary of an orthopterous larva, — Steno-
bothrus. The nuciei of these cells do not embrace nucleoli, in the sense
generally given to that word; but in the fresh condition the whole in-
terior of the nucleus appears filled with little faint “ hatchings”
(hachures) either paralle! or irregularly arranged, — an appearance such
as would be produced by bacteria. The use of acetic acid shows this
appearance to be due to straight, rod-like corpuscles which the acid
makes refringent. Under a high magnifying power each rod seems
formed of small globules united into rows. As the cells multiply the
corpuscles become successively smaller, so that the nuclei in the walls of
an ovarian chamber enclosing a nearly ripened egg contain only a mass
of fine granulations. With approaching division the rodlike corpuscles
of the nucleus become larger and less numerous; instead of being
rectilinear they present flexures, curved in various directions, or even
short ramifications. These large rods (batonnets) appear to Balbiani to
arise by the agglutination and reciprocal coalescence of the primitive
nuclear corpuscles. The cell and nucleus become ellipsoidal ; the rods
form a loose bundle parallel to the long axis of the nucleus. Then they
appear as homogeneous, cylindrical, or fusiform rods (baguettes) extend-
ing the whole length of the nucleus. Soon each is constricted in the
middle, and is then divided into halves so that two smaller bundles result
from the primitive one. These move apart along a rectilinear course,
but there is not a complete separation because a delicate filament con-
tinues to unite the halves of each rod, and taken together these fila-
ments give a distinctly striate look to the modified nucleus. The cell
: becomes narrow and elongated ; the peripheral contour of the nucleus
completely disappears, so that the body formed by the rods and fila-
ments appears plunged directly in the protoplasm of the cell and sur-
rounded at a little distance by the contour line of the latter.
_ During the separation of the two bundles their component rods _ be-
come approximated and [their substance becomes] mingled at the distal
ends, but at their proximal ends they separate from each other, so that
| each bundle takes the form of a cone, the two bases facing each other.
| The summit of the cone becomes rounded into a sort of cupola with a
)
348 BULLETIN OF THE
dentate border caused by the unfused portions of the rods. By the
constriction and division of the cell the filaments are cut in the equa-
torial plane, and withdraw into the mass formed by the rods, now
completely fused. This mass is at first homogeneous, then small vacu-
oles appear, a membrane becomes perceptible at its periphery, and the
contents are resolved into rodlike corpuscles like those which the nucleus
contained before division.
The nuclear equatorial granules were only rarely seen, and then they
took the place of the rods, each sending a filament to each pole of the
nucleus. They are only local accumulations of the substance of the rods,
which is withdrawn from the poles to be concentrated in the equatorial
region, — simple varicosities of the filaments. Balbiani was unable to
observe the radial phenomena of the cell protoplasm, on account, as he
thinks, of its great homogeneity.
Mayzen ("76°)* distinguishes two forms of nuclear division in epi-
thelial and other tissues of numerous animals which he has studied. In
one form — constantly exhibited by the endothelium of the cornea (frog)
—there is a spindle-shaped structure, which is divided, he says, into
two cones by a median transverse nuclear disk ; from this nuclear plate
numerous fibres extend to the apices of the cones, quite the same as seen
by Strasburger and Biitschli in Blatta, etc.
The rods and granules, however, which compose the nuclear disk do
not appear in Mayzel’s preparations ¢ as thickenings of the nuclear fibres,
but form, in some cases at least, a kind of ring surrounding the spindle,
the latter being composed of fibres alone. One may therefore assume,
I think, that the elements which form the nuclear disk arise from com-
pacted nuclear substance which is ezdependent of the nuclear fibres.
In the germ cells of spermatozoa in Blatta, the nuclear plate is com-
posed of granular thickenings of the nuclear fibres, just as described by
Strasburger and Biitschli. A comparison of fresh specimens with those
that have been treated with reagents (chromic acid 0.01%) shows that
the poles of the spindles, which are rounded in the fresh condition, be-
come more pointed, the nuclear fibres thicker, the whole nucleus nar-
rower, and that a clear zone is formed about the nucleus. Because this
space is artificially produced it cannot be considered a remnant of the
old mother nucleus (Eberth), in which the fibrous mass is differentiated
as a new nucleus. While the elements of the nuclear plates fuse at the
* See also Mayzel '76, "76*- 4.
+ Compare Strasburger (’77, Taf. XX XIII. Figs. 56-61), where figures of Mayzel’s
preparations are given.
MUSEUM OF COMPARATIVE ZOOLOGY. 349
poles of the spindle into two new nuclei, there is formed about each of
the latter a deeply staining homogeneous zone. It appears to be pro-
duced from the nuclear fluid, which is pressed out toward the poles, and
then consumed in the growth of the new nuclei. In no stage of the
division did Mayzel observe a radial arrangement of the protoplasmic
granules, such as is to be seen in the eggs of Ascaris.
The second form of nuclear division was seen in the endothelium from
the cornea of the frog, and the epithelium from that of the rabbit. This
appears like an hour-glass composed of fibres. The body of the cell may
either remain unaltered or may be constricted, in which latter case the
constriction closely invests the narrow part of the nucleus. The latter
corresponds to the “ Kernstrange” of Biitschli as seen on germ cells of
spermatozoa. In the corneal epzthelium of the rabbit, bird, etc. there is
formed, independently of the gradually disappearing nuclear fibres, a new
equatorial partition composed of granules. In the corneal endotheliwm
of the frog, on the other hand, there appears in the equator of the cell
between the nuclear fibres a row of small interstices or vacuoles,: which
appear to be filled with a cementing substance. It is from the union of
the contents of these vacuoles that the partition arises. A simultaneous
division of a nucleus into seven, or even into four parts (Eberth), was
never observed. All the important phenomena of the process of nuclear
division as given above were also seen in fresh preparations of the frog’s
cornea examined in aqueous humor.
The observations of Farrincer (’76, p. 607) on the division of nuclei
in epithelial cells of Petromyzon give no evidence of the existence of a
fibrous nuclear spindle.
Butscnu’s ('77", pp. 212-214) studies on the division of cartilage
cells were successful only in making it probable that the nucleus of such
cells undergoes a fibrous differentiation preliminary to constriction, and
were inadequate to establish any close relation between the nuclear di-
vision here and in the typical cases of spindle metamorphosis. He there-
: fore finds himself forced to the conclusion that a direct comparison of the
| two methods is not for the present attainable, although the similarity of
| the process to that which obtains for the secondary nucleus of Infusoria
| makes it reasonable to believe that, in the present case, one has to do
©
| with a modification of the primitive method of nuclear division.
| In a subsequent communication Mayzeu (’77*) extends his observa-
| tions to the eggs and young stages of Triton and Perca. In segmenta-
| tion spheres of the fish egg from 75 uw to 25 diameter, the figures of
nuclear division differ from those previously reported for the endothelium
tl
350 BULLETIN OF THE
of the frog’s cornea only by the presence of a distinct radial arrangement
of the granules in the cell protoplasm. The processes in the epithe.
lium of the tail of the fish embryo were essentially as in the epithelium
of the frog’s cornea. The Kernplatte were distinct, and appeared after
division like two combs with the teeth turned toward each other,
In the case of Triton the division is similar. The granules and fibres
of the modified nucleus are remarkably thick.* After division the nu-
clei take the form of fibrous baskets destitute of bottoms, and when
stained in picrocarmine appear like “gayly colored flowers.” The nn-
clear plate is wanting. The staining of the fibres in picrocarmine and
their failure to do so in osmic acid are evidences to the author that they
are simply modified nuclear substance. ‘This reaction, coupled with the
contrary deportment of the remnants of ‘“ Dotterplittchen ” to be found
in the larva of Triton, is sufficient proof of the inaccuracy of Torok’s
conclusion, that similar filamentous structures in Siredon arise by a
metamorphosis of the Dotterplittchen. Moreover, the nuclear division
is of the same nature in the fully developed Triton, where no Dotter-
plattchen are present.
Further, the direct observation of division in living cells and nuclei
(epithelium of Triton larvee) is possible. Two cells were seen to divide —
in the course of ten minutes, in one case by an advancing constriction,
in the other by means of the formation of a row of small vacuoles in the
equator of the cell. The nuclei were already divided, and appeared in
the form of a basket composed of dull lustrous rods conically arranged.
The rods become shorter, first growing more slender at the equatorial and
thicker at the peripheral end, and finally fuse into an irregular knobbed
mass. These changes of nuclear form cannot be called ameeboid.t
STRASBURGER ('77, pp. 519-521, Taf. XXXIII. Figs. 56-71) has in-
troduced into this paper several figures of Mayzel’s preparations illus-
trating division in the tissue cells of animals. The elements of the
nuclear plate (Figs. 56-58) from endothelium of the frog’s cornea ex-
hibit the same arrangement (outside the spindle fibres) which Strasburger
pointed out as sometimes existing in Nothoscordum. A well-marked
* Compare Strasburger (’77, Taf. XX XIII. Figs. 64-71) where Mayzel’s prepara-
tions are figured.
+ See also Mayzel "77 and a review (’77°) by the author himself in ‘‘ Hofmann u.
Schwalbe’s Jahresbericht,” etc.
P. S. — Another more extended paper by Mayzel (’78) is inaccessible to me, and
the short notice (Mayzel, "78%) given of it in the Jahresbericht of Hofmann and
Schwalbe is too brief to be of any value. A review of the whole is promised when
the second part has been published.
MUSEUM OF COMPARATIVE ZOOLOGY. Sanh
area surrounding the spindle figure is interpreted (see also Eberth) as
marking the limits of the unmetamorphosed nucleus, and is believed to
be filled with nuclear fluid. This area is less common in plant than in
animal cells.
The position of the nuclear [interzonal] filaments at an advanced stage
of cell division (that is, whether they converge toward the equator or
not) indicates the method by which such division is accomplished, —
whether by a constriction, or by the formation of a cell plate simultane-
ously through the whole equator of the cell, or by a combination of both
methods. In the last case a constriction advances from the periphery,
but proceeds only till it reaches the circumference of the spindle, when
its work is supplemented by the splitting of an already formed cell plate.
The two first-mentioned methods are respectively exemplified, in Mayzel’s
preparations, by endothelium from the frog’s cornea and epithelium from
that of the sparrow ; the third method, by Dicyema germs as described
by Ed. van Beneden.
_ Prremescuko ('78, "78", "78°) gives in preliminary communications
the results of his studies on cell division in the case of Triton cristatus
in (1.) the epithelium of the body; (2.) star-shaped connective-tissue
cells ; (3.) white blood-corpuscles ; and (4.) endothelium of blood capil-
laries.
The process of division is in all cases the same. In the centre of the
cell appear first small, and then large granules. These change into
thicker or more slender threads, distributed at first without order. From
the threads are produced structures which often have a quite regular
| form, — star-shaped, half star-shaped, knotted, etc. These forms are
| continually changing, and the fibres meantime are now pale, now sharply
| marked, now longer, now shorter, now finer, now thicker. They exhibit
no locomotor motion. After these changes they assume a regular cask
| shape, and become thicker in the middle. (The thickenings do not all lie
jin one plane.) The fibres divide in these thickenings, and the cask thus
| Separates into two similar portions, which at once move apart. ‘Thus the
| two new nuclei are formed. The contour of the cell then becomes sharper,
the protoplasm less transparent,— more compact, as it were, — and a
furrow, corresponding in position to the space between the new nuclei,
makes its appearance, at first on one side and subsequently on the other.
The nuclei meanwhile continue for some time to change form, and at
length the constituents of their polar ends melt together. They subse-
Lies become pale, and finally disappear.
FLEemMine ("78) gives in the present paper an extract from a lecture,
)
:
|
|
| |
352 BULLETIN OF THE
which is a preliminary report on the results of studies upon the structure
of the cell and upon the phenomena of cell division. He maintains in
all essentials the views previously expressed (see p. 264) concerning the
structure of the quiescent nucleus.
As this was not received till after his final paper (Flemming "78°) had
been reviewed, the reader is referred to the account of the latter on
page 355.
SCHLEICHER (’78")* recognizes in cartilage cells capable of, but not
undergoing division (Theilungsfihig), fibres, rods, and granules in the
protoplasm outside the nucleus. The fibres are rectilinear or curved,
often radially disposed, at other times concentrically arranged about the
nucleus, etc. The rods are shorter than the fibres, but are also often
radially disposed. The granules are most abundant near the nucleus.
All of these elements exhibit lively amceboid motion, while the nucleus
shows as yet no differentiation. This quiescent nucleus is either ho-
mogeneous with one or two clear nucleoli, or, if less homogeneous, it ig
doubtless owing to an approaching or just completed division. For
Triton, however, the presence of coarse granules and rods in the nucleus
is a permanent feature. But such structures do not necessarily inyolye
the assumption of a connected network, against the existence of which,
either in nucleus or protoplasm, the author urges the great activity of
the structures in question. Their supposed existence and the union
of intra- with extra-nuclear networks are referable to the employment
of reagents. The histologist must confine (!) himself to the living
cell in studying these phenomena. Since, in the author’s opinion, all
those structural peculiarities of the nucleus known as fibrous mass, gran-
ular mass, rodlike structures, stellar figures, glomeruli, etc. are only in-
terchangeable appearances of the same thing, viz. “nuclear substance,”
he would designate the whole series of phenomena under the head of
“‘ Karyokinesis” (nuclear motion). In the formation of the karyokinetic
figure participate granules and rods (when previously existing), nucle-
olus, new differential products, and the dismembered nuclear membrane.
No change of dimension either in nucleus or cell heralds the approach of _ |
the division. The karyokinesis consists in a series of rearrangements of | /
the nuclear substance without predetermined order, in which more or _
less regular figures are preceded and followed by such as are altogether
irregular. These rearrangements are accompanied by the disintegration
of rods into granules, and the reverse process. These changes —intro- —
ductory to the real act of nuclear division — take place with varyimg
* See also Schleicher "78.
MUSEUM OF COMPARATIVE ZOOLOGY. 853
rapidity, but have not been known to consume more than two hours.
One is not warranted in dividing the phenomena into a number of stages,
for the character of regularity is wanting. Aside from these motions
which affect the constituents of the nucleus, and are of primary signifi-
cance, its whole mass in many cases undergoes a more or less irregular
motion of translation through the protoplasm of the cell; and it may
require from three to eight minutes for the nucleus to traverse the diam-
eter of one of the larger ones. This motion ceases some time before the
division of the karyokinetic mass. Another phenomenon, observed only
in the frog, and of secondary importance, is the rotation of the nuclear
mass through an arc of 90°.
During these changes in the nuclear substance the delicate rods and
- fibres of the cell protoplasm continue their motion and gradually tend
toward the centre, where they are believed to undergo an assimilation
with the nuclear substance. By this means they become more highly
refringent, and therefore indistinguishable from the constituents of the
nucleus.
The division of the nucleus is introduced by the sudden appearance of
a parallel arrangement of the nuclear rods, which together form a some-
what elliptical cask-like figure. The rods at once divide and the halves
move apart rapidly. The immediate destiny of the halves is the consol-
idation of their constituent half-rods, and the successive forms which
may be assumed in the course of this process are quite as free from regu-
larity as are the karyokinetic figures. Between the separating halves of
the nucleus one may usually distinguish fine, clear internuclear fibres,
which, although composed of fine granules, appear as continuous fila-
ments. The author distinguishes from these other fibres or rods which
stretch between the two halves, which have nothing to do with the in-
ternuclear fibres, and which soon disappear. He has given only isolated
descriptions, which seem directly comparable with nuclear division as
observed in segmentation spheres. The single observation of a spindle
figure with equatorial accumulations of nuclear substance is interpreted
as probably an accidental product. A genuine solar figure (which, how-
ever, is interrupted for several degrees of arc), whose fine rays stretch
from the karyokinetic mass to the periphery of the cell, is distinguished
by the author from isolated groups of stouter radial fibres: the latter are
identical with the previously mentioned fibres of the cell protoplasm
(loc. cit., p. 277); the finer, on the contrary, are processes of the karyo-
kinetic mass.
The consolidation of the constituents of the new nuclei advances from
VOL. VI.— No. 12. 23
354 BULLETIN OF THE
the poles of the cask-shaped figure ; this fusion results in the production
of a homogeneous structure, which may have a somewhat irregular out-
line, — traces of its origin from distinct rods, — but which is only a tran-
sitional stage in the formation of the new nucleus. This homogeneous
structure breaks up into elements which exhibit the same irregular kary-
okinetic phenomena as the nucleus approaching division. . Ultimately a
part of the stout fibres arrange themselves to form a nuclear membrane,
which, however, does not enclose all the remaining nuclear elements, go '
that a part of the karyokinetic mass in each half is not employed in
forming the new nuclei.
A summary of Schleicher’s theoretical considerations is not easily
brought within narrow limits. The reader must therefore be referred to
the original for a complete exposition of the views entertained by the
author.
In the metamorphosis of the old nucleus into a karyokinetic mass, the |
chemical outweigh the purely physical activities ; new chemical products ~
make their appearance ; it is not a simple mechanical separation of the
less from the more fluid constituents.
The membrane and the “nuclear stuff” (i. e. the inner nuclear sub-
stance) differ chemically, for the latter must suffer a chemical change
before the two can unite. The growth of the nucleus during the karyo-
kinetic period, by which a division is made possible, is at the expense
of the enumerated protoplasmic structures ; the latter, in turn, arise by
a process of chemical differentiation, which is most active in the periph-
ery of the cell. The growth of the nucleus is not brought about by a
process of intussusception, but by the juxtaposition of visible granules.
During the protracted karyokinetic period, unknown physical forces
arise, which become recognizable at the moment of division in the sud-
den separation of the halves of the structure by repulsion. The as-
sumption that the division takes place in obedience to two centres of
attraction formed at the middle of each of the prospective daughter cells,
is negatived by the fact that the position of such centres of attraction
are conditioned by, and dependent upon, the distribution of the proto-
plasm, — the shape of the cell, in other words. It follows that in an
elongate cell these centres would lie toward the poles, and the division
would therefore have to take place in the direction of [perpendicular
to?] the longest diameter; this, however, the author’s observations
show, is not always the case.
The so-called nuclear sap is an important material, without the pres-
ence of which the homogeneous karyokinetic halves could not attain the
MUSEUM OF COMPARATIVE ZOOLOGY. 355
condition of nuclei. It is in preparation for the coming division, and for
the purpose of accumulating this substance, that all the forces of the
cell are concentrated, thus compelling a cessation of the migratory activ-
ity of the karyokinetic mass just before division. This accumulation of
nuclear fluid is a process of nutrition, effected under the attractive
influence of the nucleus, and the systems of rays are an evidence of the
existence of this nutritive process. These solar figures have, after all,
the same physiological significance, whether they are ene of stout
or slender rays.
The last structure produced by the karyokinesis — the hollow cask —
is composed of different elements. The fibres and rods divide directly,
but the contents of the cask, which are not of a protoplasmic nature,
are not capable of direct separation, owing to their viscidity ; but dur-
ing elongation fine granules, which are embraced by the cask, form
themselves into filaments. These, however, are karyokinetic granules,
which were not employed in the construction of the staves of the cask.
The last admission seems to me to remove all reasonable ground for
a distinction between the peripheral and the central fibres of the cask-
like stage of the nucleus.
New nuclei are formed, not by a differentiation of the homogeneous
mass simply, but by a disintegration brought about by renewed motion.
Notwithstanding the important influence of the nuclear sap in the for-
mation of new nuclei out of the karyokinetic halves, the latter, re-
maining unchanged, are employed in the production of the nuclear
membrane without experiencing the influence of the sap (!). The con-
struction of the membrane out of rods and granules is the cause of its
punctate appearance when seen in optical section.
The second division of FLEMmine’s (’78°) paper deals with cell division
in tissues, both normally growing and inflamed. In the division of the
epithelial cells of the caudal fin and the gill-plates of Salamandra, he dis-
tinguishes a series of phases.*
Phase 1. There arises a “basket trestle” of closely coiled, exceed-
ingly fine filaments, which gives the living nucleus the appearance of
being finely granular, and as such it has usually been described. No
evidence of nucleoli is to be found, but the nuclear figure has a sharp
limitation toward the protoplasm. As compared with the network, or
trestle, of the quiescent nucleus, it is much closer (i.e. has finer
meshes), more evenly distributed through the substance of the nucleus,
_and represents a greater mass of substance. Is it directly connected in
* The order of their succession is considered later.
356 BULLETIN OF LHE
its origin with the trestle of the quiescent nucleus, or is it a new struc-
ture? In other words, Is there, on the one hand, a complete karyolysis
(Auerbach), or a homogeneous condition (Strasburger)? or, on the
other hand, is there no such stage intervening between the network of
the quiescent nucleus and this finer trestle-work? If the former were
true, then one should at least occasionally find evidence of the existence
of entirely homogeneous nuclei. Such is not the case. Instead, one
finds on carefully prepared objects nuclei presenting peculiarities which
favor the latter view, and for the following reasons: —(a.) Such nuclei
present various degrees in the sharpness, compactness, and fineness of
the network. The finer and closer the network, the more uniform the
thickness of the filaments and the greater the tendency (especially at the
periphery) to a sinuous course. (.) In the quiescent stage the inter-
mediary substance (Zwischensubstanz) is capable of staining. In the defi-
nite glomerate stage (Knauelstadium) there is no longer any “ Zwischen-
substanz” capable of being stained. Intermediate conditions, in which
this substance has not all disappeared, correspond to intermediate stages
in the formation of the characteristic glomerule. This change appears
first at the periphery of the nucleus. Flemming, therefore, draws
the following conclusion. The first metamorphosis of the nucleus in
division consists in this, that the whole of its stainable substance, in-
clusive of that contained in the nucleoli and the nuclear membrane, is
appropriated for the nuclear trestle, which thereby grows, at first be-
coming finer, and extends itself uniformly through the nuclear space in
the form of meandering filaments; it therefore undergoes so complete a
metamorphosis, that it is no longer comparable with the trestle of the
quiescent nucleus.
Aside from these changes of the nucleus, the protoplasm of the cell
also undergoes changes. (a.) The whole body of the cell passes from a
flattened to a more nearly spherical form, — this, however, is principally
due to a corresponding change in the shape of its nucleus, — and its out-
line often becomes more rounded. (b.) A more important change is an
internal one, which exists already in this first stage, — a dicentric arrange-
ment corresponding to the future poles of the nuclear figure.* The only
* | have italicized parts of this last sentence to call particular attention to the
early appearance of this dicentric arrangement of granules in the protoplasm of tissue
cells. I must grant, it is true, that Flemming furnishes no evidence that this dicen-
tric arrangement introduces the changes of division, but that, on the contrary, it is
the nucleus itself which first exhibits changes from the quiescent condition. It,
however, will not be forgotten that Flemming’s attention has naturally been concen-
trated on the remarkable alterations in the nuclear substance, whereby the possibility
MUSEUM OF COMPARATIVE ZOOLOGY. sai 4
evidence of this is found in the arrangement of pigment granules, fat
drops, or (in the younger larval stages) remnants of the yolk granules,
which in the quiet cell lie grouped uniformly around the nucleus or
are quite irregularly distributed. ‘Wenn aber der Kern in die erste
Theilungsphase tritt, haben sie sich zu zwei Gruppen geordnet.” * These
groups in oval cells usually correspond with the poles of the longer axis,
the plane of division with the shorter axis; in some rare cases, however,
this relation is reversed. When the division-axis of the cell chances to
be very oblique to the plane of the object stage, the grouping of these
“»yolar granules” is seen less in profile, and then exhibits a distinct
radial arrangement (Joc. cit., Taf. XVI. Fig. 6 a).
Phase 2. The loose glomerate or basket form f of the mother nu-
cleus. This more open-meshed condition implies a diminution in the
number of the filaments, or, more probably, a diminution in the total
length of the filament, and is accompanied by a corresponding increase
in thickness, so that the volume of stainable substance remains the
same as in the first phase. This thickening, it is believed, is not brought
about by a direct fusion of neighboring filaments, — since no filaments
are found which are in part of their course as slender as in the first
phase, and in the adjoining part twice as thick, — but is due to a slow
process, shortening the filaments, and at the same time making them
correspondingly thicker, as in the contraction of a muscle fibre. This
of overlooking early changes in the protoplasm is greatly increased, and, what is of
more importance, that these tissue-cells can hardly be claimed to be favorable objects
for determining when the earliest appearance of a dicentric arrangement in the proto-
plasm takes place. I will not, however, insist here on the legitimacy of what I have
only ventured to call attention to in another connection as seeming worthy of more
careful attention before the initiative and controlling influence in cell division is
definitely — not to say exclusively — assigned to the nucleus (or nuclear substance).
* The words here italicized are not so in the original.
{ The basket form here spoken of is not identical with a condition of the nucleus
| thus named by Mayzel and Eberth. The structure intended by them is called by
| Flemming cask- or half-cask-shaped. It is only the staves of the cask and the ribs of
| the basket which are represented in these figures. Flemming recognizes the inapt-
} ness of the expression ‘‘ basket-form’’ (previously employed by him) to represent this
| glomerate condition for the following reason: the glomerule of tortuous filaments,
) although it is more compact at the periphery than in the centre, is not simply limited
} to bounding a cavity. On this account he prefers the name glomerule (Kniuel), even
| though this is objectionable as implying that the thread is wound about a definite
| centre, which is really not the case.
| Tf ravelled yarn be simply balled together without winding, the condition of the
| tortuous filaments will be very well reproduced ; it would only remain to make the
Mass somewhat more compact at the periphery than in the centre.
358 BULLETIN OF THE
process is, however, too slow to be directly observed in the living nucleus ;
only a series of successive drawings makes it apparent. The course of
the filaments becomes more generally perpendicular to the major axis
of the nucleus. ‘Toward the end of this phase the sharp contour, which,
in the first phase, marked the place of the nuclear membrane, is no
longer present, but there is a clear zone around the nuclear figure, which
is visible in diving, as well as in hardened cells. This, although possi-
bly more extensive on hardened preparations, is not, then, solely artifi-
cial (Mayzel). In preserved preparations delicate branched cords may
be seen to connect the periphery of the nuclear figure with the cell
plasm.
Phase 3. Star form of the mother nucleus. Just how this phase is
produced from the preceding cannot be determined on living nuclei.
Flemming believes it is accomplished through intermediate stages, the
most characteristic of which is the crown form. In the latter the course
of the filaments is almost exclusively radial, and in many cases a central
space is left entirely free ; both at the periphery and near the centre the
filaments form doops, and thus show that they are more or less continu-
ous. This hollow sphere of looped filaments gradually affects an ar-
rangement in a single plane (not that of the approaching division), and
therefore is more directly comparable with a ring, or, if the centre is not
hollow, with a disk. The peripheral loops of this crown now break
through, so that there are twice as many free ends as there formerly
were peripheral folds. The rupture need not necessarily be at the apex
of the loop. Thus the crown form passes into the star form. Already
in this stage a dicentric grouping is sometimes to be observed in the
stellar figure, since the loops which correspond to the division poles are
the first to be ruptured, those near the equator the last. Very rarely
there is a genuine double star with completely separated centres.*
Another remarkable change takes place either at the end of the pre-
vious, or during the present stage. The filaments split lengthwise each
into two. This is quite typical, at least for Salamandra. After the rup-
ture of the peripheral loops the free ends of the split filaments diverge,
and thus give rise to a jine-rayed star. This fission of the nuclear fila-
ments is not the result of the use of reagents, as it has been seen in the
living cell also. It has been observed to remain in this condition for
two hours, and meantime the stellar figure undergoes a series of slow
changes of form —a, sort of systole and diastole — which affects the
* This separation, I would add, is not to be mistaken as equivalent to the division
of the equatorial plate. .
MUSEUM OF COMPARATIVE ZOOLOGY. 359
polar rays much more than those of the equator. These oscillations have
the effect of giving the figure at the end of the systole the form of a
spheroidal body, with flattenings, or even funnel-shaped depressions, at
the poles. |
Phase 4 is of short duration, and is characterized by the formation of
an equatorial plate, during which the filament elements become grouped
parallel to the axis which is perpendicular to the plane of division. The
thickness of the plate is from one fifth to one third as great as the whole
length of the cell. At first, however, it is only the filaments in the axial
portion of the figure which are parallel, or slightly converging toward the
poles; the more peripheral are still tortuous. But this ‘ equatorial-
plate” stage, which recalls the “nuclear spindle” of other authors, differs
in several points from the typical spindle. The equatorial thickenings
known collectively as the ‘‘ Kernplatte” are wanting here,* and the fila-
ments terminate at the equator in free ends. Whether or not this equato-
rial interruption in their course is induced by an immediately preceding
division, it is difficult to say. Certain preparations which show a continu-
ity still existing between some of the fibres belonging to the opposite halves
of the figure favor the view that they were recently continuous through-
out, and yet this appearance may have been brought about by a tempo-
rary apposition of filaments which are really distinct, and were actually
separated into two groups at an earlier stage. The occasional existence
of double stars during the preceding phase strengthens the latter hy-
pothesis ; for, if the substance of the daughter nuclei in these cases was
already segregated in such a manner that each star embraced all the
nuclear substance destined for the nucleus of its own pole, then a tem-
porary apposition of the filaments must necessarily be predicated. But
if the double-star condition does not normally come in the series of
changes, it is possible that a separation of the nuclear halves may
have transpired before the equatorial-plate stage. In this connection
Flemming explains how the longitudinal fission of the filaments may
possibly be equivalent to such a separation, one half of each filament going
to one of the new nuclei, the other half to the other. This stage may
possibly be comparable with Mayzel’s spindle with outlying nuclear plate
{see p. 348). Continuous observation of this “nuclear-cask ” stage shows
that the cask becomes broader, and that its peripheral filaments become
alternately curved and straightened at the equatorial end.
Phase 5. Separation of the halves of the nuclear figure. This is
also of short duration. Each half has the form of a broad fish-weir.f
* See also Mayzel for Triton. + This is the basket stage of Eberth.
360 BULLETIN OF THE
The equatorial interval between the free ends of the filaments increases.
In the case of Salamandra there is something, like the ‘‘ Kernfaden” of
Strasburger, occasionally left stretched between the separating filaments,
but they are not continuations of the substance of which the nuclear
filaments are composed, for they are not stainable.
Phase 6. Star form of the daughter nuclei. The filaments of each
half of the nucleus — till now directed toward the equator of the cell —
begin to spread out so as to lie more nearly parallel with the equatorial
plane, and thus a somewhat flattened starlike figure is produced. The
axis of division (i. e. the line perpendicular to the centre of the plane of
division) now becomes curved, so that one or the other of these stars is
seen more en face, and then exhibits a free central space. Indications
of constriction often appear at this time on one side of the cell.
Phase 7. Crown form, and glomerule form of daughter nuclei. In
this, which resembles Phase 2 (mother nucleus), the two crown-shaped
nuclear masses have a somewhat flattened concavo-convex form, the con-
vexites being directed toward the equator. In this phase the cell is di-
vided by a continuous, constantly advancing constriction, and without
any differentiation within the cell ir the equatorial plane. That is to say,
there is no evidence of a “Zellplatte.” The central and subcentral
portions of the protoplasm are comparatively passive in this cell division.
If there is a ‘‘ contraction,” it is to be located in the cortical layer of the
protoplasm. If it is either wholly or in part a matter of attraction in
totality (Gesammtattraction) toward polar centres, then it must be said
that the grouping (readjustment) takes place so imperceptibly that its
progress finds distinct expression only at the periphery.
Phase 8 (‘if such is to be distinguished”). Trestle form of daughter
nuclei, and reversion of the same to the quiescent condition. During this
phase the nuclear filaments assume a direction perpendicular to the long
axis of the nucleus, and from that pass to a uniformly disposed trestle in
_ which the filaments are no longer curled. This becomes more and more
compact, and at the same time paler, while it increases in size. About
the beginning of this phase it also becomes sharply limited from the cell
plasm, and the intermediary substance becomes stainable. A veritable
membrane appears only after the trestle of uniformly disposed elements
has come into existence, and, as he thinks, is probably formed by a fusion
of the peripheral filaments of that trestle. The origin of nucleoli was not
discovered.
From these latter phases it is clear that the daughter nuclei have at
first a flattened stellate form; that this passes into that of a crown of
MUSEUM OF COMPARATIVE ZOOLOGY. 561
curled filaments, which are continuous by means of central and periphe-
ral loops; that from the latter arises a meandering glomerule (Win-
dungskniiuel) and from this a trestle with intermediary substance. Aside
from the double star thes zs the same series of forms assumed by the mother
nucleus, but in reverse order.
From a comparison of the whole series of changes Flemming presents
the following scheme as probably representing the double series of nu-
clear changes which accompany cell division in Salamandra, — the one
progressive and affecting the mother nucleus, the other regressive, and
(since it follows the division) pertaining to the daughter nuclei.
Mother nucleus Daughter nuclet
(progressive). (regressive).
1. Trestle (quiescent). 1. Trestle (quiescent).
y t
2. Fine-thread glomerule. 2. Fine-thread glomerule.
| i
8. Thickening of the fine threads and 3. Narrowing [of the coils].
4 loosening of the coils.
4. Central and peripheral loops (crown 4. Central and peripheral loops (crown
¥ form). * form).
(Rupture of the loops. ) (Union into loops ?)
5. Star form of mother nucleus. 5. | Star form of daughter nuclei.
Coarse-rayed half-cask.
v }
6. Fission of its rays. 6. Fusion of rays in pairs (?).
y +
7. Fine-rayed star. 7. Fine-rayed, half-cask.
8. Equatorial plate.
Results on other cells are mostly confirmatory of the changes given
above. However, in connective-tissue cells an incomplete division results
in a cell having two nuclei; this is more rarely seen in epithelium. In
red blood-corpuscles the nuclear filaments so increase in extent as to reach
to near the periphery of the cell. The author thinks the cell substance
has in this case contributed to the remarkable increase in the bulk of
the nuclear figure, and finds an argument to support this view in the fact
that filaments of the nuclear figure in wnstained chromic acid prepara-
tions have a peculiar greenish brown or brownish yellow color correspond-
ing to that of hemoglobin. This, he adds, would be a striking confir-
mation of Auerbach’s theory of the mingling of nuclear substance and
cell substance in division, were it not that the substance of blood-cells
is very peculiar as compared with that of other cells, and that in other
cells such a phenomenon does not take place.
362 BULLETIN OF THE
The points in the metamorphosis of the nucleus to which Flemming
has here called attention for the first time are :— (1.) the first stage,
which is not granular, but presents a connected system of curled, very
fine filaments ; (2.) the delicate glomerule stage which immediately fol-
lows ; (3.) the loosening in the coils; (4.) the stage with peripheral and
central loops; (5.) the rupture of the loops to form a star; (6.) the
fission of the filaments ; (7.) a bipolar arrangement of the figure during
a series of rhythmical contractions and expansions; (8.) the fact that
the daughter nuclei do not at once form a homogeneous mass, but pass
in reverse order through the stages which the parent nucleus undergoes
during the metamorphosis. _
The objections which Auerbach (’'76) has raised against identifying
the spindle- or nuclear-figure with the mother nucleus are answered by
Flemming point by point :—(1.) the nuclear figure is not always larger
than the quiescent nucleus, and in cases where it is larger the old nu-
cleus has already before division so increased in size that the masses of
both nearly agree ; (2.) the sharp nuclear membrane, it is true, is lost,
but the nuclear figure still remains sharply limited from the cell plasm ;
(3.) there is no stage found in Salamandra where the old nucleus has
actually or apparently disappeared, but the nuclear figure is morphologi-
cally derived from it; (4.) the new nuclei do arise from a division of the
old nucleus. It remains, however, to ask, says the author, whether in
the formation of the nuclear figure anything is taken from the protoplasm,
whether anything of the substance of the nucleus goes at this time to the
protoplasm, and, finally, if any like change takes place during the growth
of the new nuclei. All three suppositions are possible. It is certain
that the clear substance between the curled filaments does not directly
go to the new nuclei. One cannot, then, hold to a complete identity of the
nuclear figure with the nucleus. In red blood-corpuscles a large part of
the cell substance, in fact, almost the whole of it, is incorporated in the
division figure. If this is not the case in other cells, it can hardly be
denied that a small part of the substance of the nuclear figure is an-
nexed from the protoplasm. An exchange between nuclear substance and
plasma as a general phenomenon is, if not proved, at least to be assumed
as possible. Fol, Auerbach, and the author himself, says Flemming,
have rightly maintained that a cell division in Remak’s sense does not
cover the facts, but they have as certainly fallen into error in maintain-
ing that no formal element of the nucleus remains.*
* ‘Dass ein solcher Kern bei der Theilung nicht bestehen bleibt (i. e. as mem-
brane, contents, and nucleoli) und sich nicht direct entzweischniirt, dass also die alte,
MUSEUM OF COMPARATIVE ZOOLOGY. 363
Flemming dissents from the general views expressed by Strasburger
(76 and 77) as follows : —
(1.) The nucleus is not always elongated at the beginning of division.
(2.) It is not homogeneous before division.
(3.) A polar opposition at two peripheral points of the nucleus is
formed in the “ Anfangsstadien,” as is shown by the grouping of the
“polar granules” in the plasma; but this polarity does not here (Sala-
mandra) come to the morphological expression in the nuclear mass itself,
which Strasburger lays down as a general principle. The poles, in these
animal cells, are not characterized by a special refractive power. “ Wah-
rend die Polkirner schon lange gruppirt sind, besteht noch keine dicentrische
Ordnung in der Kernfigur.” There follows, rather, a radial (monocentric)
grouping — the star form — which finds no place in Strasburger’s scheme.
At least, there is no visible expression of an accumulation of part of the
active nuclear substance at the poles, anda repulsion of another part
toward the equatorial plane, in this stage, nor yet in that of the forma-
tion of the ‘‘ equatorial plate” (Flemming), inasmuch as at this time the
whole of the substance to become new nuclei is collected at the equator.
I have given in some detail Flemming’s views in this connection, be-
cause they seem to confirm in a very decided way certain of the conclu-
sions at which I had already arrived from the study of entirely different
objects, and on somewhat different grounds. It cannot fail to impress
one as rather remarkable that there should be no evidence of a bipolar
condition in the nucleus when the protoplasm was already thus distin-
guished, if, as has generally been believed, it is nuclear substance, which
constitutes the centres about which the dicentric arrangement finds ex-
pression. Evidently the tissue cells, which afforded the material for his
study, are not the most favorable objects for determining the exact posi-
tion of the centres about which this polar grouping of plasma granules
takes place. Perhaps the eggs of Limax may help to explain why this
early grouping ensues. Iam inclined, in view of the possibility that the
centres of attraction may be at first phenomena of the cell plasm and
not of the nucleus, to suggest that these centres may also in tissue cells
lie totally outside the nucleus, as differentiations in the protoplasm. I
attach little weight to the supposed absence of a special refractive power
of the poles, since, for two reasons, it may have been overlooked ; namely,
Remak’sche Lehre von der Zelltheilung nicht zutrifft, darauf haben Fol, ich und
Auerbach mit vollem Recht aufmerksam gemacht; und mit ebenso vollkommen
Unrecht haben wir angenommen, dass vom Kern wirklich nichts Geformtes restire,
weil es an unseren Objecten nicht zu sehen war.”
364 BULLETIN OF THE
the unfavorable nature of his objects for determining the exact position of
the centres of attraction, — for the granules are very scanty and of com-
paratively large size, — and the fact that he was especially interested in
a confirmation (or negation) of Strasburger’s view, whereby his attention
was directed to an accumulation of active “ Kernstoff” in this vicinity.
The evidence to be gathered from Flemming’s paper as to the exact
condition of the nuclear membrane when these polar figures of the proto-
plasm jirst appear, is not absolutely decisive in favor of the view that the
centres of attraction are formed quite independently of nuclear substance,
although his own conclusions are positive. (/oc. cit., p. 364) in excluding
the possibility of a mingling of nuclear mass and protoplasm at this
stage.* The fact that the dicentric arrangement in the protoplasm is not
shown on the figures of stained preparations (except at a much later stage)
makes it the more difficult to form a just idea of the temporal relation
of these two series of phenomena, — the plasmic and the nuclear. How-
ever, Flemming assures us (in the explanation of the plates) that the
stage reproduced in Taf. XVI. Fig. 2 a (where the appearance of the di-
centric arrangement is first figured) corresponds to the stained specimen
(Taf. XVII. Fig. 3) to which the description just pointed out refers.
This seems to indicate the same conclusion as must be drawn from Fig.
52 of Limax, where the nuclear membranes of both pronuclei are still ©
intact, sharply defined, double-contoured structures, and where one of the
polar stars has already made its appearance. It is certainly difficult to
conceive how any formed substance could, in this case, have come to
occupy such a position outside the nuclear membrane. I cite this figure
for two reasons: the egg was hardened in chromic acid (not in acetic
acid, which has been thought to produce an artificial appearance of the
nuclear membrane), and the sections were all preserved, so that I can
say with positiveness that only one stellar figure was recognizable in
this case. This is of importance in showing a closer approximation to
the first appearance of the stellar figure than most other observers have
made, and therefore serves to justify my conviction that their conclu-
sions may, at least in some cases, rest upon insufficient observations.
* ‘‘TDagegen besteht noch jetzt eine scharfe Abgrenzung der Kernfiguren gegen das
Plasma, allerdings nur an gefarbten Objecten (Taf. XVII. Fig. 3) sicher zu stellen
als ein feiner, aber scharfer Contour. Derselbe kann aber mit der alten Kernmem-
bran nicht mehr identisch genannt werden, denn er ist zarter und nicht immer so deut-
lich, wie sie, tingirbar ; vielleicht ist er ein Rest von ihr, vielleicht nur der Ausdruck
der Grenze zwischen Kernmasse und Plasma, — aber es ist Gewicht darauf zu legen,
dass diese Grenze auch noch in diesem Stadium eine scharfe, eine Vermischung von
Kernmasse und Plasma also fiir dasselbe noch jedenfalls auszuschliessen ist.”
MUSEUM OF COMPARATIVE ZOOLOGY. $65
Flemming finds in his studies nothing to homologize with the ‘‘ Kern-
spindel,” and therefore concludes that division may take place in the
cells of animal tissues without such a structure. In Triton and Sala-
mandra nothing of the interzonal filaments (Kernfaden, Strasburger) or
the cell plate has been discovered. So, too, the thick fibres which Stras-
burger calls in Nothoscordum fragrans “‘ Kernspindel” are really homolo-
gous to the whole stainable nuclear figure, and are therefore comparable
with ‘‘ Kernplattenelemente ” rather than the spindle.
In view of Peremeschko’s statement that in Triton there are equato-
rial thickenings in the cask-shaped structure, and of Schleicher’s recog-
nition of interzonal filaments, these conclusions of Flemming are less
convincing. One may still entertain a doubt if, after all, we should not
recognize in some of the stages seen by Flemming (e. g. Taf. XVII.
Fig. 14) the equivalent of spindle and nuclear plate combined.
Flemming emphasizes the fact that the stellate or monocentric condi-
tion of the nuclear substance is not to be confounded with a stellate
figure of the cel/ plasm, and yet that the two are so similar that it would
seem extremely improbable that they were such merely by chance. He
says, ‘It seems to me hardly deniable that the yolk radiations as well
as the stars represent a visible expression of the forces which at that
particular time are active in the cell substance and nuclear substance,
and which operate according to a monocentric-radial type before the di-
vision, a dicentric-radial type after the division.” (Joc. cit., p. 422.)
It does not seem to me that his own observations justify a conclusion
which makes the forces effecting both these conditions identical, and the
figures themselves the successzve expressions of the same continuous force.
Viewing the cell as a whole, they are not simply successive phenomena ;
they are co-existing. The changes in the nuclear substance lead from the
monocentric to the dicentric condition, and so far there is a succession,
: in the manner suggested ; but with the cell as a whole it seems much
_ More as though there were two distinct (though analogous) and in a sense
antagonistic forces, —one acting from the centre of the nuclear substance
| and finding expression in the monocentric condition of the same; the
other acting from the stellar poles in the cell plasm and ultimately domi-
nating, till, with the effected division, the first or nuclear force is en-
abled to reassert its supremacy. In this connection I must repeat what
‘has been so many times said, that the centre of the new nucleus (the
/ Seat of the nuclear force) is not identical in position with the centre from
be the forces of the cell plasm operate. It is possible that this hy-
pothesis may account for the oscillations (systole and diastole) observed
;
}
5
{
’
\
366 BULLETIN OF THE
by Flemming to take place in the nuclear substance ; for these oscilla-
tions occur at a time when the monocentric may be supposed to be giy-
ing way to the dicentric attraction.
y-. Plants. — A part of the spindle metamorphosis of the nucleus, —
namely, the equatorial plate, — appears to have been seen at an earlier
date in the division of vegetable cells * than in that of animal cells. The
real significance of the disk was overlooked, however, in the belief that its
components were artificial products, — alterations produced in the albu-
minous fluid of the middle of the cell by the protracted action of water.
Russow (’72) was the first to correct this mistake, and to establish, in
the year succeeding the appearance of Kowalevsky’s paper, and quite in-
dependently of his discovery, the normal existence of granular zones in
certain plant cells similar to those seen by Kowalevsky. These were the
parent cells of spore and pollen elements. The observations in the case
of ferns were made only after a study of the less obscure structure in
Ophioglossum and Equisetum. It was in these that the nuclear plate
(Kernplatte Strasburger) was for the first time accurately observed, but
the less conspicuous spindle fibres were not seen. The relation of the
plate to the nucleus was, however, very cogently argued. The separated
halves of this nuclear disk were also seen, but not fully understood, nor —
their mutual recession suspected. It was pointed out that the nuclear
plate, and the structure afterwards called by Strasburger cell plate, were
not identical, so that what is said (/oc. ct., p. 51) concerning the “ Korner-
platte” (cell plate) in the formation of spores in Marsilia is in no sense
to be referred to the nuclear structure mentioned.
Russow’s statements (pp. 89, 90) are as follows: “ Neben Mutterzellen
von dem geschilderten Aussehen [i. e. with a very large, finely granular,
spherical nucleus, usually eccentric in position], findet man (bei Polypod.
vulgare und Aspid. Filix mas) andere, die statt des Kerns eine kreis-
formige Platte von } bis # Durchmesser der Mutterzelle fiihren, deren
Fliche grob granulirt, deren Rand, wenn man auf denselben nach Dreh-
ung der Platte um 90° herab sieht, wie aus linglichen Kornchen, oder
kurzen Stabchen, die hell und stark lichtbrechend sind, zusammengesetzt
erscheint. Grdsser und schirfer ausgepragt sind diese Kérnchen- oder
Stibchenplatten in den Sporenmutterzellen der Ophioglosseen und Equi-
setaceen (Figs. 121, 122, 123, 126); am gréssesten und in ihrem Bau
am deutlichsten erkennbar fand ich die Platten in den Pollenmutterzellen
* Hofmeister, Die Lehre von der Pflanzenzelle (1867, p. 82, Figs. d.ande). See
also the explanation of the figures.
MUSEUM OF COMPARATIVE ZOOLOGY. 307
yon Lilium bulbiferum (Fig. 152); hier bestehen sie aus kurzen, verhilt-
nissmiissig dicken, wurmférmigen Kérperchen oder schwach gekriimmten
Stibchen, die farblos, hell und matt glanzend sind, und durch Jod kaum
merklich gefirbt, durch Alcalien (selbst bei grosser Verdiinnung) car-
minsaures Ammoniak und Chlorzinkjod fast momentan aufgelost werden,
ohne sich zu farben. Dasselbe chemische Verhalten zeigen die Platten
bei den Ophioglosseen, Equisetaceen und Farnen.
“Diese Stibchenplatten . . . . sind durchaus verschieden von den
s. g. Kornerplatten oder Protoplasmaplatten, die nach dem der primire
Kern geschwunden und 2 neue (secundire) Kerne erscheinen, zwischen
letzteren auftretend die Sporenmutterzelle halbiren, oder, die nach dem
Erscheinen der 4 tertitiren Kerne auftreten, um die Sporenmutterzell-
wande zu bilden. Aus dem Umstande, dass zur Zeit, wo Stabchenplat-
ten vorhanden, nie Kerne sichtbar sind, und dass . .. . nach dem
Auftreten der die Mutterzelle halbirenden Kornerplatte zu beiden Seiten
letzterer, wo sonst die Kerne vorhanden, je eine Stabchenplatte (von
dem halben Durchmesser der primiaren Stabchenplatte) sichtbar ist, darf
man wol auf eine nahe Beziehung zwischen Kern und Stiabchenplatte
schliessen, wenn nicht auf die Bildung letzterer aus ersterem. Bei Poly-
pod. vulgare und Aspid. Filix mas habe ich nur in wenigen Fallen nach
dem Auftreten der Kornerplatte zu beiden Seiten derselben Stiibchen-
platten wahrgenommen, doch glaube ich, dass ihr Auftreten hier wie in
den Sporenmutterzellen der Farne und Gefasskryptogamen itiberhaupt
und wahrscheinlich auch im den Pollenmutterzellen der Phanerogamen
eine regelmissige Erscheinung ist, die nur in den meisten Fallen wegen
ihrer Kleinheit und anderer ungiinstigen Umstiande halber sich der
Beobachtung entzieht.”
The following is from the detailed description of the Stabchenplatte
in the case of Ophioglossum vulgatum (pp. 126, 127): “ Die Stiibchen-
| platten sind selten ganz eben, meist ein wenig gewolbt oder am Rande
| verbogen ; am besten erkennt man ihren Bau, wenn ihre Fliche zu der
| Sehaxe des Auges ein wenig geneigt steht; werden sie durch einen
| ziemlich starken Druck aufs Deckglass alterirt, so tritt ihre Zusammen-
setzung aus verbogenen Stabchen oder wurmférmigen Kérperchen * be-
| sonders deutlich hervor.”
' The succeeding changes are: (1.) the disappearance of this primary
| disk (Staébchenplatte) ; (2.) the appearance of two (secondary) nuclei of
|
about half the size of the primary nucleus; (3.) the appearance of a
“ Kornerplatte ” (cell plate) between these ; (4.) the appearance of two
)
* Compare pp. 355 - 362 (Flemming).
\
}
)
|
|
7
j
368 BULLETIN OF THE
(secondary) disks in place of the nuclei, smaller than the primary disk ;
(5.) the disappearance of the secondary disks; (6.) the appearance of
four (tertiary) nuclei in positions corresponding to the four angles of a
tetrahedron.
Of the secondary disks, it is further said that their surfaces are either
(a) parallel with, or (6) perpendicular to, the Kornerplatte, from which
it may be justly inferred that the author mistook in the first case (a)
the mutually receding lateral, halves of the primary disk for second-
ary disks, and that only those having the position indicated under (6)
were really secondary structures. He says concerning the latter that
they may lie in the same plane, or their planes may be mutually per-
pendicular. The latter arrangement evidently corresponds to the tetra-
hedral disposition of the four nuclei, which result from the division of
these two disks.
In the Equisetacee (p. 148) “numerous stages of transition between
these disks and the spherical cell-nucleus, with respect to the size of the
whole structure as well as the rods (Korperchen) which compose it, are
observable.” 7
As Strasburger has already pointed out, TscuistiaKorr (75) was the
first to observe in plant cells the fibrous differentiation of the nuclear
spindle. The account which he ((oc. cit., col. 20) gives for the mother —
cells of the microspores of Isoétes Durieui, is essentially the same as that
for Lycopodium and Equisetum (col. 24, 25). In Angiopteris (col. 7),
where the spindle figure was not observed, the protoplasm during the
division of the cell is entirely homogeneous, without any such morpho-
logical differentiation as nucleus and nucleolus. Inasmuch as these are
visible when the cell is subjected to the influence of water, he offers
the following as an explanation of the phenomena. The plasma un-
dergoes several steps of chemical metamorphosis, which begin at the cen-
tre of the cell contents. The inner plasm absorbs more water than the
more peripheral portions, because it is in a more advanced state of
chemical metamorphosis, and thereby the optical properties of the parts
become so different that the inner one becomes distinguishable as a nu-
cleus, whereas before the action of the water it had no definite bounda-
ries. Therefore, nucleus, nucleolus, and primordial utricle are only so
many successive steps in the process of metamorphosis.*
This seems to be very nearly equivalent to saying they have no mor-
* See also Tschistiakoff, Notice préliminaire sur Vhistoire du développement
des sporanges et des spores de l’Isoétes Durieui, Bory. In Nuovo Giornale Botameo
Italiano, Tom. V. p. 207. |
———— ee
a
es
gy: em
MUSEUM OF COMPARATIVE ZOOLOGY. 369
phological importance! For this indistinguishable “ physiological nu-
cleus” Tschistiakoff employs the term pronucleus.
In Isoétes this ‘‘ pronucleus,” under the influence of water, exhibits,
according to Tschistiakoff (col. 20), the form of an ellipsoid, or, rather,
appears to be composed of two cones placed base to base ; the long axis
corresponds with that of the cell; the substance of the pronucleus is
differentiated, so that one sees upon its surface more or less compact
lustrous streaks, which are arranged as meridians. These streaks
(“ Differencialia”) are apparently spindle fibres, and his “ pronucleus
striatus” is the so-called spindle figure, or nuclear spindle. In a more
advanced stage, he continues, an equatorial welt of still more compact
substance is to be observed on the surface of the “ pronucleus.” This is
simply a plasmatic plate composed of projecting papilla, through which
the plasm is divided in its physiological centre. At this time there are,
two small protoplasmic spheres near the poles of the “ pronucleus”
[central areas of asters?] which are soon converted into small vacuoles
[the equivalents of Biitschli’s multiple nuclei ?], — the “ pronuclei” of
the two new parts. The plate which divides the “ pronucleus” appears
in the form of a welt, because it is more compact than the rest of the
“pronucleus.” This structure subsequently extends to the other parts
of the protoplasm ; the division proceeds from the centre toward the
periphery. The division of the protoplasm ensues in consequence of the
molecules becoming grouped according to their polarity. From this it
is evident that the groups, being in nature alike, must separate by rea-
son of the force of mutual repulsion.
The formation of macrospores out of the mother cell in the case of
Isoétes is similar to the formation of spores of Anthoceros. The mother
cell has a morphological nucleus. The groups of starch granules are not
held, as formerly,* to be nuclei; the secondary nuclei are not formed
in the presence of the primary nucleus, although the masses of starch
are. In the vicinity of the latter, innumerable transparent protoplasmic
filaments diverge in all directions. By the crossing of these filaments in
the middle of the cell there arise compact uniform plates [cell plates],
which, like the starch granules, have a tetrahedral arrangement, and
which serve, by their fission, to divide the cell into four portions. Four
secondary nuclei are found in the centre of the mother cell, each corre-
Sponding to a cluster of starch granules. They are, however, much
nearer the planes of division, and are formed in the cnterior of the pri-
mary nucleus, which is subsequently dissolved.
* See Nuovo Giornale Botanico Italiano, Tom. V.
VOL. VI.—NO. 12. 24
370 BULLETIN OF THE
This differs in several particulars from the more recent account given —
by Strasburger.
In pollen mother-cells of Magnolia and Conifera a nuclear spindle has
also been seen by Tschistiakoff; but the description is so confused
through the introduction of imaginary “pronuclei” and “ pronucleoli ”
as not to be easily understood. In Magnolia, the equator and the poles
of the ‘‘ pronucleus” become more compact. The equatorial lamella be-
comes broader, and exhibits a meridional striation. The substance of
the two poles represents the two prospective ‘ pronuclei,” during the
enlargement of which the striation becomes indistinct. Each of the two
resulting secondary ‘ pronuclei” possesses two nucleoli. Each of the
“‘ pronuclei ” now divides, and so quickly that the act is almost simulta-
neous with the first cell division.
In conifers after the nucleus has again assumed the condition of a
“pronucleus” there appear either one or six very fine protoplasmic
division-lamellz. This is an indication of the division of the “ pronu-
cleus” either into two parts, or at once into four, which then have the
tetrahedral arrangement. Furthermore, both “pronucleus” and “ pro-
nucleolus” are very peculiarly streaked upon the surface by a multitude
of serpentine lines consisting of more compact and lustrous portions of
the pronuclear substance.* These lines become changed into broad,
compact, brilliant bands in the form of projecting meridians. The equa-
torial division-plate of lustrous protoplasmic corpuscles becomes broader.
Two protoplasmic regions, representing the prospective secondary nuclei,
now make their appearance at the poles. The streaked equatorial zone
persists for some time, but finally the streaks disappear, and the two
new pronuclei are separated by a wide zone of protoplasm. The “ pro-
nuclei” are soon converted into nuclei.
It will be seen that Tschistiakoff has not made a sharp distinction in
his description between cell plate and nuclear plate, and that the broad-
ening of the equatorial zone is the only thing that even hints at a mi-
gration of the halves of the nuclear plate.
The criticisms of AuveRBacH ("76*) are directed toward the views ex-
pressed by Strasburger in the first edition of his celebrated work, “ Ueber
Zellbildung und Zelltheilung.” As that edition has not been formally
considered in the present paper, the reader is referred to the review of
the second edition, to be found at pp. 372 et seg. Auerbach has now
observed that the middle piece of his karyolytic figure is more spindle-
shaped than previously (1874) represented by him, and that it has a
* Compare Flemming’s ("78) descriptions of the nuclei of animal tissue-cells.
MUSEUM OF COMPARATIVE ZOOLOGY. Syd
meridional striation ; but this, he thinks, in no way invalidates his pre-
viously expressed views.
In two points he dissents from Strasburger’s conclusions: (1.) the
process of the neoformation (Neubildung) of nuclei; (2.) the method of
their increase. He maintains that the nucleus is at first a sort of vacu-
ole, —a droplike accumulation of a “ dickfliissig,” clear, homogeneous
substance, in a cavity of the protoplasm, which has at first no special
limiting layer. Subsequently, the protoplasm in immediate contact
with the surface of this nuclear drop becomes compacted into a special
“ Wandung,” —the nuclear membrane, —and one or several nucleoli
are formed by a gradual agglomeration of finest spherules. He believes
Strasburger’s view — that the nucleus is only a more or less sharply seg-
regated portion of the cell protoplasm — rests upon a misconception of
the true nature of the structures which he has called “ cell” and “ nu-
cleus ” in the endosperm cells especially of Phaseolus multiflorus. Ac-
cording to Auerbach these are respectively nucleus and nucleolus. This
revision of Strasburger’s conclusions he endeavors to substantiate by an
examination of the properties of the structures in question. In the first
place Strasburger’s “nuclei” are typical nucleoli, which, in small nuclei,
are always dark, solid spherules in the centre of the nuclear space, and
which undergo the changes ascribed by Strasburger to his ‘ nuclei,’ —
becoming often irregularly pointed and vacuolated, whereas nwclec are
uniformly clear bodies in dark protoplasmic surroundings. Again, his
“cell” cannot be a cell, since from the beginning it is a vesicle (Hohl-
bliischen), whereas a free-formed cell is never a vesicle at first. The
radial appearance and netlike structure of this “cell” are not necessarily
to be homologized with the netlike distribution of protoplasm so com-
mon in plant cells, since the same morphological condition is also known
to exist in the nucleus of many (animal) cells.* Finally, there exists
between these free-formed “cells” portions of the protoplasm of the
mother cell. If the wall of the vesicle is the ‘ Hautschicht ” of a cell,
one must assume that this protoplasmic mass, in which the cellulose
membrane is formed, intervenes between the Hautschicht on the one
hand and the cellulose membrane on the other ; but that would be alto-
gether anomalous.
The views here expressed concerning nuclear division are substan-
* Auerbach does not consider the network in this case to be composed of the same
substance as nucleolus and nuclear membrane ; instead of being nucleolar substance,
it is of the same material which in other nuclei makes its appearance in the form of
discrete spherules, — his so-called Zwischenkiigelchen. Compare Auerbach 74.
312 BULLETIN OF THE |
tially a repetition of those already given in another paper. Sec pp. 304,
305. In addition, he maintains (p. 22) in regard to the spindle that
two things have been confounded. <A portion of the meridional lines are
only rows of dark granules imbedded in the cell protoplasm, which lie
at the surface of the spindle in the territory of the radial expanse of the
karyolytic figure. With the use of a low magnifying power, or after
employing hardening reagents, the yolk granules which are closely
packed in the intervals between the rays that stretch from pole to pole
(spindle) may have the appearance of continuous meridional lines.
I do not believe the filaments of the spindle in Limax can be ac-
counted for in this way. There are no interfilamentous rows of proto-
plasmic granules in the territory of the spindle, but the spindle fibres
themselves are, if not in the beginning, eventually much thicker than
the extra-spindle rays.
Auerbach, for the sake of brevity, would substitute “‘ Karyolyma ” for
“karyolytische Figur.”
Incidental to a criticism of Tschistiakoff’s use of “pronucleus” for the
physiological nucleus, which subsequently becomes a morphological nu-
cleus, he suggests that the at times apparently striate middle portion of
the karyolyma may better be called cnternucleus. This, however, seems
to rest on a misconception of, or refusal to recognize, the essential na-
ture of the nuclear disk and its separated halves.
Among botanists, it is SrraspurceR (76) to whom are due the most
extensive contributions in this line of research.
Led, by the study of alcoholic preparations of embryos of the pie
family, to the conclusion that before cell division the nucleus undergoes
radical morphological changes, he successfully endeavored to control
his observations by the close study of some living object on which the
inferred metamorphoses might be followed step by step. He had come
to the conclusion, from the study of alcoholic specimens of successive
stages, that the nucleus before cell division becomes elongated, more or
less ellipsoidal, and presents in its equator a peculiar plate composed of
a single layer of nearly parallel rodlike granules ; that, further, to both
sides of this plate bands (Streifen) are attached, which converge toward
the poles of the nucleus, thus lending to the latter a spindle-like appear-
ance; that subsequently the plate of rods (Stiibchenplatte) becomes
split into halves which, by mutually receding, approach the poles of the
nucleus, but leave stretched between them numerous fine Kernfaden
[interzonal filaments]. The substance of the halves after migrating
toward the poles of the spindle forms two new nuclei, one for each of
MUSEUM OF COMPARATIVE ZOOLOGY. Sie
the two daughter cells (pp. 26, 27). Such was Strasburger’s conclusion,
when he undertook its confirmation by the study of cell division on the
fresh-water alga, Spirogyra. His results (pp. 34-37, 42-48) may be
summarized as follows.
In the normal quiescent condition of the Spirogyra cell, the nucleus
appears fusiform, with its axis perpendicular to the axis of the alga fila-
ments.* The first change in a cell about to undergo division is a thick-
ening of the nucleus. This is accompanied by a commotion in the
enveloping granular protoplasm. The latter stretches out from the ends
of the now cylindrical nucleus in the form of suspensory filaments. At
length the nucleus has increased its thickness fourfold, and its nucleolus,
at first increased in size, has entirely disappeared. Suddenly, after the
solution of the nucleolus, the substance of the nucleus exhibits a fila-
mentous differentiation, which proceeds from the lateral surfaces toward
the equatorial plane. At the same time it becomes condensed in the
equatorial plane into a highly refractive plate (Kernplatte). This cen-
tral plate exhibits no structural differentiation in the fresh condition, but
in alcoholic preparations it shows a continuation of the parallel striations
of the lateral halves of the nucleus; but in the middle the bands are much
thicker, and appear like short rods, which are separated by intervals equal
to their own thickness. The plate is disk-shaped and reaches. to the pe-
riphery of the nuclear mass. The whole striated nuclear structure is
surrounded by a hollow cylinder of finely granular protoplasm, leaving
exposed only the ends of the nucleus. The insertion of the nuclear fila-
ments (Kernfaden), as seen from the end of the cylinder, embraces a cir-
cular area, and presents a finely stippled appearance. Simultaneously
with these nuclear changes the first evidence of the approaching division
appears in the mural protoplasm of the cell.
By further changes this striate nuclear structure becomes elongated in
a direction corresponding to the length of the filaments, with accompa-
nying decrease of diameter, and assumes the shape of a cask. Granular
protoplasm collects at the ends of the cask-shaped nucleus; the thick-
ness of the nuclear disk becomes increased by the lengthening of its com-
ponent rods, each of which now shows a median constriction. In this
way the nuclear plate begins to divide into lateral halves (Plattenseg-
mente). These plate-segments separate so rapidily that the motion may
be directly observed with a magnifying power of 600 diameters. In the
Separation the halves of the component rods move apart, but drawn-out
filaments'[interzonal filaments] of their substance serve still to unite their
* Jt in reality has the form of a biconvex lens.
374 BULLETIN OF THE
swollen extremities. The whole cask-shaped nucleus undergoes a length-
ening meantime, so that the two segments have made only comparatively
little advance toward the ends of the nuclear structure. Both the nu-
cleus and the surrounding protoplasm are in great commotion, and the
latter is often radially disposed at the ends of the nucleus (p. 44). There
appears a granular accumulation in the equatorial plane of the [inter-
zonal] filaments, and into this median zone the latter are at length ab-
sorbed. About this time the protoplasm, which ensheathed the sides of
the nucleus, is differentiated into a few (ca. 15) filaments [not nuclear
filaments !], which are attached behind the disks (i. e. on their polar
faces) in a circle.
When the interzonal filaments disappear, the granules of the lateral
segments begin to fuse with each other and with the striated nuclear sub-
stance (nuclear fibres) which still remains between this structure and
the ends of the lengthened cask-shaped nucleus. Thus solid disks are
formed. The latter soon move into contact with the granular protoplasm
which covers the ends of the cask-shaped structure. Each of the extra-
nuclear filaments * soon presents at both its extremities — in the granular
protoplasm covering the polar surfaces of the nuclear disks —a little
swelling, and at the same time the course of the filaments becomes more
convex outwardly. The equatorial granular accumulations of the inter-
zonal filaments are ultimately transferred to these extranuclear filaments,
and they in turn unite with the ingrowing girdle of mural protoplasm.
Meantime the equatorial faces of the homogeneous solid disks become
convex ; there soon appears in each disk a few (2-4) highly refractive
globular bodies, all but one of which are gradually dissolved and disap-
pear ; this one increases in size and becomes the nucleolus; it eventn-
ally comes to occupy the centre of the nucleus (disk), both faces of the
latter having meantime become convex. By the distribution of the gran-
ular protoplasm over the whole surface of the two new nuclei, the latter
are in all essentials like the nucleus from which they were derived.
With this more detailed account for Spirogyra the other studies of
Strasburger on plant cells may be summarized by considering some of
their deviations from the case just reviewed. Besides alge the cells
of various higher plants were studied, principally by means of alcoholic
preparations. Stomatic and endosperm cells, the parent cells of pollen
and spores, the hairs of Tradescantia stamens, etc., exhibited essentially
* By this name I would designate those filaments which are formed from the
protoplasm lying outside the cask-shaped nucleus, and which Strasburger calls *‘ Ver-
bindungsfaden.”’
MUSEUM OF COMPARATIVE ZOOLOGY. 315
the same phenomena. Aside from differences in the prominence of the
separate features which are to be made out from a comparison of these
results, the following variations may be mentioned. The form of the
nuclear structure may vary greatly in different objects, from the almost
truncate cask-shape to the very pointed spindle, as, for example, in the
parent spore-cells of Psilotum (Taf. VI. Figs. 86, 90), or Equisetum (Figs.
102, 105, 107); but advanced stages usually exhibit in all cases a very
plump outline. The nuclear plate may be homogeneous, as though formed
by the complete consolidation of its rodlike bodies (Allium, pp. 137, 138,
and Taf. VI. Figs. 55, 56); the rods may be few (Taf. VI. Fig. 53), or
numerous, large, and closely approximated, as in Psilotum (Taf. VI. Fig.
87). The interzonal filaments increase in number and in size, as, for
example, in the parent cells of pollen in Allium (p. 138) and Tropzeolum
(p. 140), of spores in Equisetum (p. 149), and of macrospores in Isoétes
(p. 158) ; but owing to the smallness of the nucleus, they do not always
become convex enough to reach the wall of the parent cell. The gran-
ular accumulation in the equator leads to the formation of a continuous
structure, the cell plate (pp. 27, 111, etc.), in which is differentiated
the cellulose partition of the two new cells. The halves of the cell
plate, not receding from each other to any such extent as did the
halves of the Kernplatte, form the ‘‘ Hautschicht” of the young cells.
Inasmuch as the nuclear structure does not always swell in its equator
sufficiently to meet the wall of the parent cell, this cell plate may be
supplemented by a similar structure in the surrounding protoplasm
(Plattenschicht im Protoplasma, pp. 28, 111, 113, etc.) continuous with
it. The adjacent protoplasm may then show a fibrous differentiation
(see Taf. IT. Fig. 30) similar to and parallel with that of the nucleus.
Thus both nucleus and cell protoplasm may operate conjointly in accom-
plishing the formation of the new boundary, or, as in Spirogyra, they
may act simultaneously, but separately, for the accomplishment of the
same object. Only a single nucleolus makes its appearance in the new
nuclei of Ulothrix, while in many nuclei peculiar differentiations appear
in the form of granular bands running parallel to the spindle axis (p. 27,
Taf. II. Figs. 29, 30), or granules are arranged (pp. 96, 119, 138, Taf. V.
Figs. 28, 37, and Taf. VI. Figs. 62, 65, 110) in the equator of the new
nucleus, in a plane transverse to the axis of the spindle.
The process of division is somewhat abbreviated in the case of the
formation of spore and pollen cells. The nucleus of the parent cell is
divided, with the formation of a “ Kernplatte,” into two, and the “ Zell-
platte” is indicated ; but before a cell wall can be formed the two new
376 BULLETIN OF THE
nuclei again divide in the same manner, so that the wall of all four cells
is formed almost simultaneously, although the division of the parent
nucleus was by two successive steps.
Still more remarkable is the abbreviation which prevails in the forma-
tion of spores in Anthoceros, and makrospores in Isoétes, for here the
spindle filaments are formed between two masses of protoplasm, while
the parent nucleus still retains its form, but the usual nuclear plates
are not produced. Each of the protoplasmic masses (potentially, though
not formally, a nucleus) again divides, without forming a nuclear plate,
and in each of the four masses arises a single nucleus, not, however,
until the parent nucleus, after remaining thus long, has finally dis-
appeared. These abbreviated forms of division serve as a possible expla-
nation of the phenomenon of free cell-formation. In the case of Picea
vulgaris, for example, after dissolution of the “‘ Keimkern” (equivalent
to the nucleus of the first segmentation sphere in animals), normally
four cell nuclei arise simultaneously in the upper end of the “egg” (p.
21). These exercise an influence on the surrounding protoplasm, which
is thus made to assume a radially striate appearance about the nuclei as
centres. The boundary of the four corresponding cells then makes its
appearance, and what is left of the substance of the egg-cell furnishes to
these four cells (or their descendants) alouminous matter. In the case —
of another conifer (Ginko biloba) there are as many as thirty new nu-
clei, which simultaneously take the place of the primary nucleus, and
about these, as centres, all the protoplasmic contents are divided into a
corresponding number of cells.
In the formation of free endosperm cells of Phaseolus multiflorus the
nucleus and cell make their appearance at the same tume, — not the nu-
cleus first, as has usually been maintained,—the former in almost
punctiform size, the latter as a clear, circular zone surrounding the for-
mer. Both increase in size: the zone often exhibits a radiate arrange-
ment of protoplasmic particles about the nucleus as a centre. The
nucleus remains for some time homogeneous, and then several vacuoles
simultaneously make their appearance. The protoplasm of the cell
becomes reticulate; the nucleus assumes an eccentric position; the
protoplasm finally takes the form of a thin, granular mural layer, free
from vacuoles; the cells, by their increase in size, come into mutual
contact ; and it is only then that a cellulose layer is to be discovered.
The radial structure of the zone surrounding the nucleus in the case
of the “ Ei” of Ephedra — where the free cell-formation is much like
that of the last case —is particularly distinct, and the protoplasm of
|
|
MUSEUM OF COMPARATIVE ZOOLOGY. Evil
each new cell exhibits a differentiation into a more compact portion
immediately surrounding the nucleus, and a peripheral, less compact
portion.* The nucleus differentiates a nuclear membrane and nucleoli
of varying size, and the cells produce a cellulose envelope before their
mutual contact.
In his “ General Results and Considerations,” based on animal as well
as vegetable cells, Strasburger discusses first the stellate phenomena.
In free cell-formation there are in operation forces which, acting from a
central mass, attract most of the molecules of the surrounding proto-
plasm, but repel a small part of them, namely, those which compose the
“ Hautschicht.” These are molecular forces, and the radial arrange-
ment of the protoplasm favors the view of a polarity of the protoplasmic
molecules. In the eggs of animals, at the first formation of the “ Keim-
kern,” it is surrounded with rays. It is by means of these rays that the
nucleus pushes itself away from the peripheral Hautschicht, until, having
reached the centre of the egg, it remains in equilibrium with its rays,
reaching out to the Hautschicht on all sides. It may remain in an
eccentric position only when the sphere of its operation is too limited to
cause it to take the central position.
It seems to me unfortunate for this explanation that the influence of
the nucleus, as expressed in the length of the rays, should in some cases
diminish as it nears the centre of the egg. How, too, will it be possible
to explain the migration of the male pronucleus when, as in Limax,
there are no protoplasmic rays to push it from the periphery ?
The function of the nucleus, he says, is made most obvious in cell di-
vision. It becomes homogeneous, then an opposition between two points
of its surface is developed. These points mutually repel each other, and
a lengthening of the nucleus is the result. Certain components of the
“Kernsubstanz” are repelled from each of the two poles, and are col-
lected simultaneously to form the nuclear plate. In proportion as the
substance of the nuclear plate recedes from the poles, a striation is dis-
tinguishable behind it. These changes within the nucleus induce the
radial alterations in the surrounding granular protoplasm. The changes
_ in the form of the cell are accomplished by the influence of the nucleus,
but only when the rays have reached the surface of the protoplasm
(Ascidia).
Although the “ Kernfiden” do not seem to have in animal cells an
extensive development or well-marked function, in plant cells they
* This recalls the condition of the eggs of certain echinoderms, quite recently de-
scribed by Ed. van Beneden and Selenka.
378 BULLETIN OF THE
increase in number and volume, and are employed for the construc-
tion of the cell plate. Their exact signification in the formation of
the “ Hautschichtplatten” may not warrant his earlier (first edition)
conclusions as to the identity of nuclear substance and, “‘ Hautschicht.”
He is now inclined to believe that there is simply an accumulation
of ‘“ Hautschichtmasse ” between the Kernfiiden, especially since the
Hautschichtplatte is formed in some places without the assistance of
these filaments; the real signification of the latter may, perhaps, sim-
ply be to guide the substance necessary for the formation of the plate
in the proper courses, and possibly to afford (mechanical?) support to
the plate. From the manner in which the Hautschicht is preformed
along the future plane of division in plant cells it is certain that it can-
not be compared to the denser layer produced at the surface of liquids
by superficial tension. He also thinks the “ Einschniirungstheorie” ig
disproved by this observation.
Strasburger can hardly be justified in extending the latter conclusion
to animal cells, especially since there is clear evidence of an infolding of
peripheral substance in cases (e. g. Rana) where pigment, at first limited
to the superficial portions of the cell, follows the deepening constriction.
The splitting of the cell plate ensues certainly under the influence of
the two nuclei, perhaps from reasons similar to those which cause a
splitting in the nuclear plate.
Although he claims for the nucleus a controlling influence in the
process of cell division, he is compelled to admit in certain cases (spores of
Anthoceros, macrospores of Isoétes, etc., where the old nucleus is “‘ pushed
to one side and finally dissolved,” while the function of division is as-
sumed by an “ Attractionsmasse” which is individualized near by) that
the nucleus has lost its power of division. The explanation given is
that new nuclear substance has been collected about the old nucleus, and
has assumed the function of the latter.* The necessary phyllogenetic
connection of this with the more typical division is at once demonstrated
by the fact that the nearest relatives of these plants (indeed, the mzcro-
spores of the same Isoétes plant) exhibit the normal method of cell
division in their spores.
I have no objection to considering, with Strasburger, this modified
form of division as the result of independent adaptations (induced, per-
haps, by the same causes) in each of the cases which he cites; but I
cannot consider the process so fundamentally different from the typical
* “Tn der That sahen wir diese am Kern angesammelte Masse mit ihren Starkeein-
schliissen sich ahnlich wie sonst die Substanz der Kerne bei der Theilung verhalten.”
MUSEUM OF COMPARATIVE ZOOLOGY. 379
method as he does. Our differences of opinion result from different
conceptions of the ré/e of the nuclear substance during division, — of the
nature of the ‘‘ Attractionsmasse,” in other words. It follows from the
passage which I have just quoted, that he considers the two (afterwards
four) starch-containing masses as nuclear substance. I believe, on the
other hand, they are accumulations of ce// protoplasm — the equivalents
of the so-called aveas—about centres of attraction, and that the dis-
tance of these centres from the old nucleus is only another argument
tending to show what I have already suggested, that the centres of
attraction may perhaps at first be quite independent of nuclear sub-
stance. I think it will be at once apparent that from this standpoint
there is not so wide a gulf separating the two processes as appears from
Strasburger’s interpretations. It no longer becomes necessary to assume,
with him, the existence of a zew nuclear substance, to which are trans-
ferred the functions of the old nucleus, while the latter maintains a
separate existence. Nor are we forced to look upon the dissolution of
the old nucleus as essentially different from the metamorphosis which
takes place in the typical case. Barring the assumption that the cen-
tres of attraction are nuclear substance, the metamorphosis consists
essentially in the transfer of nuclear substance in two (or more) direc-
tions toward centres of attraction. That such a transfer of nuclear
substance (from the old nucleus) also takes place in these exceptional
cases must be granted, I think, from Strasburger’s own words, for he
says (p. 158): “ Der Mutterzellkern wird aber inhaltsiirmer, wahrend
seine Hautschicht dicker und granulirter erscheint (Fig. 3); endlich
_ schwindet er vollstandig. Es fallt dies sein Verschwinden mit der Zeit
zusammen, in der die Zellplatten gebildet werden. ... . Um diese Zeit
beginnt aber auch erst die Differenzirung der Zellkerne in den vier Proto-
plasmamassen. Die Anlage beginnt immer seitlich von der Stairkemasse
und zwar, so weit sich dies noch sicher stellen lisst, auf derjenigen Seite,
welche der letzten Theilungsfliche zugekehrt ist.” From this I can
only conclude that the dissolution of the old nucleus is accompanied by
a transfer of its substance toward the four centres of attraction near
| which it is employed in the formation of the four new nuclei. That
| these new nuclei lie on that side of their respective starch-enveloping
| masses which was last in union with a cognate mass, only serves to
| confirm one in assuming that a part of this nuclear substance had been
| transferred to the vicinity of the “ Attractionsmasse” before the second
| division of the latter ensued ; that assumption, moreover, seems in no
|
)
| way to conflict with the statement that the old nucleus was at this time
380 BULLETIN OF THE
becoming “inhaltsirmer.” Whether this transfer of substance is accom-
plished in the form of visible granules, in any way comparable with a
nuclear plate, seems doubtful from Strasburger’s description ; but if his
studies were confined to alcoholic preparations, it would have been very
easy, even for so accomplished an observer, to have overlooked nuclear-
plate stages, which are always of comparatively short duration. I do
not, however, wish to express any opinion on this point, without the
personal observations necessary to an independent judgment. May it
not be, however, that Tschistiakoff’s ("75) statement —that the nuclei are
found much nearer the planes of division than are the clusters of starch
granules to which they correspond —is based upon the observation of
stages in the migration of a nuclear plate (his nucleus), which were not —
seen by Strasburger? The latter observer, it is true, states that the
nuclei lie at first in contact with the cluster of starch granules, and sub-
sequently move away from the latter. So far as I know, however, such
a migration away from an “ Attractionscentrum ” has not been observed
by others.
In Strasburger’s opinion the least modified methods of cell division
are such as prevail when the whole cell contents are granular proto-
plasm, and the nucleus is central. Here the nucleus plays an important
réle (through the interzonal filaments) in the formation of the cell wall. —
All other causes are, to a greater or less extent, modifications of this.
It is shown, further, that the share which the nucleus has in this process
may be gradually diminished, and for it may be substituted the activity
of the mural protoplasm. The formation of the cell partition may thus,
in place of being semultaneous, at length be brought about by the succes-
sive steps of an ingrowth from the mural protoplasm. The function of
the nucleus in cell division has thereby suffered a reduction, and an ulti-
mate condition is to be found in such cases as Cladophora,* where the
* P.S.—Scumitz (79) has brought forward evidence to show that, contrary to
the opinion held by Strasburger, the bodies which he (’76, p. 87) saw in Cladophora,
and designated as ‘‘halbkugelige Anhaiufungen kérnigen Protoplasmas,” are really
cell nuclei.’ Schmitz has shown, among other things, that they behave like nuclei
when treated with reagents, and has followed them during division, in which, how-
ever, he has been able to gain only unsatisfactory evidence of a filamentous differen-
tiation. An elongation always takes place prior to division, and a diminution in the
intensity with which the body stains is at this time accompanied by a gradual mass-
ing of the nuclear substance at the two poles. The nuclear division is positively not
accompanied by a division of the protoplasm, so that from the uninuclear germ
there results first one and then a number of multinuclear cells. He corroborates
Strasburger in making the cell division, when it does occur, quite independent of
these nuclear structures.
|
MUSEUM OF COMPARATIVE ZOOLOGY. 381
nucleus has become superfluous, and has consequently disappeared en-
tirely from the development.
The substantial identity of cell division with plants and animals
allows Strasburger to conclude that cell formation is induced by the
same forces throughout the whole realm of organized beings. Whether
this identity justifies the conclusion that animal cells and plant cells are
homologous, —that consequently animals and plants have a common
origin, — is much less certain. It is not possible, a priori, to positively
deny that the successive events of cell division are an «mmediate me-
chanical necessity. The latter cannot, for the present at least, be de-
monstrated ; but its possibility once granted, it is clear this agreement
in the succession of events no longer serves as evidence of a direct
(genetic) relationship between the objects under consideration.
Other processes of cell formation —freie Zellbildung, Vielzellbildung,
Vollzellbildung (or, better, Einzellbildung)— are to be considered as
abbreviations of cell division. Successive stages in this process of
abbreviation are demonstrable. For example, in the egg of the Abie-
tineze the four cells which are formed after the dissolution of the old
nucleus about four newly made free nuclei are arranged just as though
they had been formed by the repeated division of an apical cell. This
presents a case less removed from normal division than is that where
(Ephedra) the resulting cells no longer retain any definite topographical
relationship. The spores of the Ascomycetz are produced by free cell-
formation, namely, a dissolution of the nucleus of the mother cell and
the semultaneous appearance of as many secondary nuclei as there are to
be spores; but in some cases it has been shown that the necessary
number of nuclei arise by successive dichotomous division. The ex-
tremest modifications are such as occur when the old nucleus is not
dissolved before the beginning of the free cell-formation, but is pushed
| to one side and remains unemployed, while new cells arise out of a part
: of the protoplasm of the mother cell, as is exemplified in the formation of
| the “ Keimblaschen ” and their “Gegenfiisslerinnen” with metasperms.
| A somewhat similar case (Isoétes) I have considered above, and am
‘not entirely satisfied that this last one may not also be found on closer
“study to diverge less from the normal method of cell division than we
E warranted in concluding from Hofmeister’s investigations.
| Animals afford less opportunity for the study of “free cell-formation ”
a plants, and it may appear hazardous to venture any suggestions as
ie @ possible point of comparison. There is, however, in the embryology
of some animals a method of cell production which appears to be closely
382 BULLETIN OF THE
related to this process of free cell-formation, — which is to a certain ex-
tent intermediate between cell division and the latter. I refer to the
formation of nuclei (by division) in. homogeneous masses of protoplasm
which do not at once (perhaps never) respond to the nuclear division by a
division of their substance, — e. g. segmentation in Eupagurus Prideauxii
(P. Mayer, ’77). Such potential cells (autoplasts, Lankester ; entoplasts,
Whitman,) differ, as regards their origin, from the free-formed cells in
that their nuclei demonstrably arise by division. It seems to me not
impossible that the free cell-formation of botanists may ultimately be
found to be much more restricted than at present believed ; that it may
be possible, namely, to demonstrate the existence of stages of division
in the nucleus which have hitherto been overlooked or mistaken for its
dissolution. I strongly suspect that such is at least the case with
Strasburger’s observations on the cell division of Isoétes. The excep-
tional cases with Ascomycetz point in the same direction. If such a
restriction of free cell-formation should be realized in plants, the differ-
ences in the secondary modifications of ‘cell division in plants and ani-
mals would not be so divergent as they at present appear.
Strasburger takes occasion, in considering Auerbach’s views of the
nature of the nucleus, to expand his own ideas. He practically distin-
guishes three sorts of “‘ Kernsubstanz”: one is an active kind, which is’
collected at the “‘ poles,” and is thereby divided into two antagonistic
portions ; another is repelled by these poles, and collects as a median
nuclear plate ; and a third kind, not repelled by the substance of the
poles serves, in the form of filaments, to join the latter with the median
plate. The maximum removal of the poles from the nuclear plate seems
to be soon attained ; but as the poles continue to repel each other, it re-
sults that the nuclear plate is thereby divided into halves. He concludes
that the nuclear plate plays a passive ré/e, since a median portion of the
same is drawn out in the form of fine [interzonal] filaments.
I do not fully agree with these conclusions. Strasburger himself
grants that the ‘nuclear poles” are “in stofflicher Beziehung von der
iibrigen Kernmasse verschieden,” in that they are more highly refractive.
It is therefore an assumption when he says the “ poles” consist of nuclear
substance. It is unsatisfatory to assume that the substance of the nu-
clear plate acquires its equatorial position in virtue of a repulsive influ-
ence exercised on it by the “poles,” since it leaves unexplained how it
is that the same substance subsequently approaches these “poles.” The —
nuclear fibres are probably not exclusively nuclear substance, since it 18
demonstrable that they in some cases arise outside the nucleus, and it
MUSEUM OF COMPARATIVE ZOOLOGY. 383
is perhaps even more questionable if any part of the interzonal filaments
is nuclear substance.
Other points of his descriptions and conclusions agree much better
with my own observations. As regards the formation of the new nuclei
in the segmentation spheres of animal eggs, he gives the following in
many particulars excellent summary, parts of which I take the liberty
to italicize: “‘Im Kern folgt aber dem geschilderten Zustand derjenige
seiner definitiven Ausbildung, die mir in dem Gange, welche sie in sich
furchenden thierischen Eiern einschligt, besonders instructiv schien.
Da beginnt nahmlich von der friiheren Segmentseite an die homogene
Kernsubstanz sich in dichtere und minder dichte Bestandtheile zu schei-
den ; die dichteren bilden das Licht stirker brechenden Kernkorperchen,
die minder dichten schwacher das Licht brechenden, die Grundmasse des
Zellkerns, in der die Kernkorperchen schweben. Um diese Zeit ist der
Kernpol noch erkennbar und weisen die umgebenden Strahlen noch auf
‘denselben hin, er scheint sich also nicht [direct] an der Bildung der Kern-
kérperchen und der Grundmasse des Kerns zu betheiligen, auch ist er
von der so differenzirten Stelle durch den homogenen Theil des Kerns
getrennt. rst wenn die beschriebene Differenzirung im ganzen Zell-
kerne vollendet ist, beginnt auch die Substanz des Kernpols sich zu
vertheilen und gleichzeitig schwindet das homogene, ihn umgebende
Zellprotoplasma und die von letzerem ausgehenden Strahlen. So lange
der Kernpol und das thn umgebende Zellplasma sowie die Zellstrahlen nicht
ganz geschwunden, behauptet er auch seine Stellung und kann der ganze
Zellkern noch nicht in seine Stelle riicken. Die Polsubstanz scheint sich
in der Grundsubstanz des Zellkerns zu vertheilen, ohne besondere Form-
elemente desselben zu bilden. Freilich ist es nicht leicht Letzteres fest-
-zustellen, doch mochte ich fast darauf schliessen, erstens aus dem schon
erwahnten Umstande, dass die Differenzirung der Kernsubstanz in Grund-
masse und Kernkorperchen schon vor sich geht, wenn die Polsubstanz
noch als solche unterscheidbar ist ; zweitens aus der wiederholt von mir
bei Unio und ein Mal auch bei Phallusia beobachteten Erscheinung, dass
\die Ansammlung der activen Kernmasse an den Polen ausnahmsweise [1]
beginnen kann vor Auflisung der Kernkirperchen, bezichungsweise der Kern-
‘hiille, bevor also die Substanz des Kerns homogen geworden ist.”
| Ifhe were to admit that the two centres of attraction are not poles of
the nucleus in all cases, and were to grant that the ‘“ Kernsubstanz” of
‘ithe poles is not of necessity nuclear substance, then our views would not
‘differ widely. I cannot assent, however, to the relation which the new
‘nucleus is made to hold to the centre of attraction at the early stages
|
384 BULLETIN OF THE
of its formation. I see it a shape substantially as Strasburger has
figured it (doc. cit., Taf. VII. Fig. 21, and Taf. VIII. Figs. 9, 12), —a
pear-shaped body with its blunter end directed toward the plane of seg- |
mentation (Limax, Fig. 80°), but in positeon it is quite different. The
more pointed end does not correspond to the centre of attraction (“ Pol”)
as he represents it, but is removed from the “ Pol” half the long diam-
eter of the nucleus at a time when several nucleoli have made their
appearance. This distance makes the more certain the conclusion of
Strasburger, that the ‘‘ Pol” furnishes no “ Formelemente”’ to the grow-
ing nucleus, and has suggested the possibility that this central portion
of the “area” might not be nuclear substance, and that it might not
enter into the composition of the new nucleus, but become finally dif
fused in the protoplasm of the yolk.
The differentiation of the nucleus into more and less dense portions is
not so clearly localized as in Strasburger’s Fig. 21, Taf. VII., although
the nucleoli are here (Fig. 80*) more abundant at the blunt end. The
peculiar form I would explain as brought about by the continued attrac-
tion of the so-called Polsubstanz upon the nucleus combined with the
increasing opposition offered to its actual progression by the increasing
density of the protoplasm nearer the centre of the ‘‘area.” * The sub-
sequent assumption of a more nearly spherical form would then be but
the natural result of a gradual diminution of the attractive force, further
evidence of which is seen in the gradually fading rays of the protoplas-
mic aster. Strasburger is ‘‘ convinced that the form of the cell nucleus
is to be taken as the expression of the forces operating in its interior.”
With that conception the peculiar pear-shaped form now under consider-
ation could not easily be otherwise explained than as I have suggested
in the foot-note, for the “ Polsubstanz” most certainly at this time forms
no part of the zntertor of the nucleus. A corresponding relationship of
“centre of attraction” and nuclear bodies is shown for the pronuclei of
Limax in Fig. 68. This seems to me a confirmation of the view which
makes the peculiar form due to the attractive influence of substance
which lies outside both the pronuclei, and which also induces a stellar
figure in the surrounding protoplasm.
The most serious obstacle to the view which I have suggested is found
’
in the formation of free nuclei, where, to make use of Strasburgers
* In view, however, of the automatic form-changes of which the nucleus is cer-
tainly at times capable, it may not be erroneous to look upon this pointed extremity
as a sort of pseudopodal prolongation, having an important function in the nutrition |
of the nucleus from the substance of the ‘‘area.”’
MUSEUM OF COMPARATIVE ZOOLOGY. 385
words, “the active Kernstof is uniformly distributed in the remaining
Kernsubstanz,” as far at least as the optical evidence goes. While this
does not necessarily preclude the notion I have maintained, it certainly
gives a great appearance of accuracy to the view which recognizes in this
active (attractive) substance an essential part of the nucleus. Strasbur-
ger, however, is compelled still to recognize a separate active “ Kernstoff,”
without disclosing to us any of its properties save those which are mani-
fest by the radial phenomena. It therefore seems to me equally justifi-
able to apply to this active substance any other name than nuclear
substance. If one may call it nuclear substance because it is here sur-
rounded by or distributed through nuclear substance, then with equal
propriety it may be called in nuclear division a protoplasmic (vitelline)
substance.
The importance of this substance which forms the centre of the aster
(“Kernsubstanz”) is thus formally announced by the author: ‘ Meine
ganze Auffassung gipfelt in der zum Theil in dieser Auflage erst scharf
formulirten Behauptung, dass von der activen Substanz an den Kernpolen
die ganze Structur der Kerne und die Kerntheilung, dre Structur des umge-
benden Zellplasma und dann die Zelltheilung bestimmt wird.”
In a subsequent paper Strasburger (’77, p. 518) calls attention to a
case (Nothoscordum) in which the spindle fibres are exceptionally delicate,
and the nuclear plate is represented by rodlike elements arranged in
part around (outside) the equator. From this he concludes that the
elements of the nuclear plate are not simple swellings of the fibres, and
that in this particular case their repulsion from the poles was so forcible
as to result in their elimination from the spindle.*
TrREvB (’79) has contributed interesting observations on the réle of the
nucleus in the division of plant cells. His observations were made mostly
on the phanerogams, and especial attention was given to following the
steps of nuclear changes in living cells examined in a comparatively in-
_ different fluid. The time which intervenes between the different stages
figured is given. These observations are supplemented by studies of
alcoholic preparations stained in picrocarmine.
The formation of the nuclear plate is accomplished (e. g. in the
| ovules” of Epipactis) without the intervention of a homogeneous con-
| dition of the nucleus. The latter, at first finely granular and containing
| asingle nucleolus, at length contains a limited number of coarse, dis-
| tinct, irregularly disposed granules. After the lapse of some time these
|
1 %
gradually accumulate at the middle (equator) of the nucleus to form di-
* See also p. 350.
| VOL. VI. — No. 12. 25
386 BULLETIN OF THE
rectly the nuclear plate, in which they lose their individuality. This
migration and confluence of the coarse granules is accompanied (always?)
by a marked contraction of the nucleus.
In the division of the nuclear plate and the separation of its halves,
there appear first a narrow dark line through the middle of the band
(the disk seen edgewise), and then several detached, lenticular clear spaces,
which at length become confluent and thus effect a complete separation —
of the halves. The latter move apart, rapidly at first, afterward with a
gradually retarded motion ; they become thicker, but less definitely out-
lined, the farther they move away from each other. They remain united
more or less by irregularly placed bands of threads, which for an instant
may form a bundle of parallel striations. Usually the nuclear plates
remain parallel, but in one case (Fig. 7) it was observed that the central
portions of the disks became widely separated while their peripheries still
remained close together.*
During the latter part of the migration of the halves of the nuclear
plate, the old nucleus (its outline is no longer sharply distinguishable
from the enveloping protoplasm) undergoes a change of form and size,
It elongates, then it becomes broader till it sometimes touches the wall
of the cell; but later its diameter undergoes a considerable reduction.
The nucleus finally becomes cylindrical, and at the same time the halves
of the nuclear plate become gradually rounded, and may now be called
secondary nuclei. Still later, minute granules in active motion are seen
to make their way toward the middle of the space between these two
secondary nuclei. They arrange themselves in a transverse layer, — the
beginning of the cell plate. Whence they arise is uncertain, but since
they move in all directions it is hardly possible that they glide along
invisible filaments stretched between the two secondary nuclei.
In Crinum asiaticam Treub has seen the nuclear mass differentiated
into rods (Fig. 27).f instead of granules, from which the nuclear plate
is formed. The homogeneous condition of the nucleus before the forma-
tion of the nuclear plate is far from being general.
Trenb disagrees with Strasburger as to the methods in which the cell
* Were it not that Trenb’s sketches presented in this case stages quickly sueceed-
ing each other (Figs. 7° to 7* = 20 min.), I should be inclined to think that his Fig. 7°
was the representation of a single annular nuclear disk seen somewhat obliquely.
The signs of division shown in Fig. 7° seem to preclude that view. I am induced by
these observations to again call attention to Fig. 24 of Bobretzky’s ("76) paper, and
to admit that possibly a similar condition to that seen by Treub is the basis of this
figure, which I have endeavored to explain in quite another manner.
+ Compare Strasburger ’77, Taf. XX XIII. Figs. 55-58.
z
MUSEUM OF COMPARATIVE ZOOLOGY. 387
plate and cellulose membrane are formed. He says (p. 28): “(1.) The
cell plate, formed in the ‘cask’ between the two young nuclei, grows
at its edges until it touches the walls of the cell on all sides. (2.) Never
have I seen the cell plate formed in the cask completed by a ring ema-
nating from the cell wall; neither have I ever seen an annular membrane
of cellulose rise up to encounter the cell plate.” Thus the rdle of the
nucleus is much more important than Strasburger admits. It is by the
direct intervention of the young nuclei that the whole cell plate, and
consequently the whole of the cellulose membrane, is formed.
From a consideration of all his own observations he concludes that
the filaments and striations in or between the nuclei (nuclear fibres and
interzonal filaments) are of secondary importance, at least in the cell
division of the higher plants.
2. Maturation.
The fate of the germinative vesicle has been a matter of ardent dis-
cussion since 1850, yet it is only within a very recent period that suff-
ciently varied methods of investigation have been employed to make the
attainment of a final decision probable. But increased facilities of study
have not led to unanimity of opinion among those who have carefully
followed the changes which overtake this structure.
It is now very generally conceded that the germinative vesicle, like
the nucleus of an ordinary cell,* suffers a remarkable metamorphosis.
By some observers this metamorphosis is claimed to be only a rather
fundamental rearrangement of the constituents of the vesicle, without
their general dispersion ; by others, that it is so radical as really to in-
volve a total dissolution and a distribution of the nuclear matter. To
this latter conception the term metamorphosis can be applied only in its
broadest sense ; on the other hand, the first conception is not held to
entirely preclude either the loss of old, or the acquisition of new matter
in the process of transformation.
* A general discussion of the morphological value of the germinative vesicle can-
not be attempted here, especially since the origin and growth of the egg, which has
formed no part of my studies, must of necessity constitute an important portion of the
evidence to be considered in such a discussion. I may state, however, in this connec-
tion, that quite recently a view, which at one time obtained very general acceptance,
has been revived by Brandt, Villot, and others. They claim that the germinative
vesicle is entitled to rank as a ced/ rather than as a nucleus.
Without attempting to refute at length their position, I wish to emphasize the fact
that the germinative vesicle sustains the same relation to the first maturation spindle
that an ordinary nucleus does to the spindle which takes its place.
388 BULLETIN OF THE
These two views more or less closely reproduce the opposing ideas held
by the earlier embryologists. An extended review of those earlier opin-
ions is rendered unnecessary by the labors of recent investigators, espe-
cially Oellacher, Flemming, Fol, O. Hertwig, Biitschli, Ed. van Beneden,
and Whitman. The different views group themselves naturally under
one or the other of three heads, according as it was claimed that the
germinative vesicle disappears, or persists and undergoes division, or,
finally, that only the germinative dot remains while the vesicle suffers
dissolution.
, Although it has often occurred that the same author has arrived at |
opposite conclusions in the study of different animals, it does not follow:
that differences of opinion can in general be referred to the actual exist-
ence of differences from one species to another ; on the contrary, it has
been possible for the study of the same species to lead to the most diver
gent conclusions.*
But if the germinative vesicle does not persist and undergo division to
form the nuclei of the first pair of segmentation spheres, what becomes of
its substance? This question has had various answers. Purkinje (30,
p- 15), the discoverer of the vesicle, entertained the opinion that, inas-
much as it was not to be found in (hen’s) eggs taken from the oviduct,
it became ruptured by the contractions of that organ, and that its con-
tents, a “lympha generatrix,” became mingled with the germ. It was
owing to this supposed germinative influence of the contents that the
vesicle was thus named. Von Baer (’27), who was the first to show that
a migration of the vesicle takes place in the hen’s egg from the centre to
* In the case of the rabbit, for example, Bischoff (42, pp. 38, 39, 75-77, 141)
concludes that the germinative vesicle, which exists as a protective envelope to the
germinative dot up to the time of impregnation, disappears, and that the dot under
the influence of the male element undergoes division, the two parts becoming the
centres about which the yolk is grouped to form the first pair of segmentation spheres.
Ed. van Beneden (’70, pp. 178, 179), on the contrary, holds ‘that the disappearance
of the germinative vesicle is apparent rather than real, just as it is an untenable posi-
tion to maintain that the nuclei of segmentation spheres, because they become pale,
homogeneous, and transparent, disappear and are replaced by new nuclei. Also at
p- 244 (doc. cit.) he says: “En résumé je considére non comme démontré, mais comme
trés-probable que la vésicule germinative se divise au lieu disparaitre, et que ses por-
tions deviennent les noyaux des deux premiers globes vitellins.”
Bischoff (’45, pp. 22, 42, ’52, pp. 20, 21) subsequently modified his views in so
far as to consider the persistence even of the germinative dot as problematic, and Van
Beneden (76%, pp. 39, 40, and "76", p. 154) now goes so far as to assert that his ‘*re-
searches on the ovum of the rabbit have proved. . . . that no morphological part of the
germinal vesicle is found in the yolk at the moment of fecundation.”
MUSEUM OF COMPARATIVE ZOOLOGY. 389
*
the periphery, and probably also in the case of other animals, held nearly
the same opinion concerning its fate and function.* Its disappearance,
however, was not due to the contraction of the oviduct, but resulted
from the maturation of the egg. Van Bambeke (’76, pp. 116, 117) has
recently described for batrachians a “claviform figure,” which indicates
the course pursued by certain parts of the germinative vesicle at the time
of their expulsion from the egg. The dilatation at the internal end of
the club-shaped figure corresponds to the place occupied by the germi-
native vesicle at the moment of its disappearance, after which event one
finds at the superior pole of the egg traces of the expelled portions. He
is not able to say what parts are expelled, and what remain in the
vitellus.
The dissolution and elimination of the vesicle has been very generally
believed in by those who have followed the development of vertebrates
other than mammals, and in a modified form has recently had an able
advocate in Oellacher (72). This author has endeavored to harmonize
the phenomena observed in mammals with his own careful observations
on the trout egg, by considering the so-called polar globules of the for-
mer the equivalent of the contents of the germinative vesicle in the trout.
The latter assumes, as he has discovered, the shape of one or two sphe-
roidal masses at the time when the membrane of the germinative vesicle
is everted and spread on the surface of the germ. He concludes ((oc. cit.,
pp. 24, 25) that the germinative vesicle in all vertebrates’ eggs, as they
approach maturity, migrates to the surface and is ejected from the germ ;
that in no vertebrate is there a genetic connection between the vesicle
and the nuclei of the first segmentation spheres; and that the same is
possibly true of all animals, as observations on the eggs of mollusks
would help to prove.
In the opinion of these and many other authors the vesicle (or parts
of it) is eliminated in an amorphous condition, or promptly becomes such
and then vanishes. Not widely different from this view is the opinion
which early gained credence with students of. invertebrate embryology,
connecting the germinative vesicle with the formation of discrete sphe-
roidal bodies, first observed in the case of mollusks,t which are detached
from the vitellus as “ polar globules.”
* “Post fecundationem verum blastoderma eo loco evolvitur, quo vesicule humor
effusus est.” (Loc. cit., p. 29.)
t So far as I know, such a structure was first figured by Carus (24, Taf. IV. A. a).
However, he gives no very intelligible description of it in the text. Several years
later, Dumortier (’37, pp. 10, 11, 15, and Pl. I.) saw such bodies, two in number,
390 BULLETIN OF THE
we
But among those who have insisted on the derivation of the polar
elobules from the germinative vesicle, there has been considerable diver-
‘sity of opinion. As we have just seen, Dumortier held the globules to
be the vesicle itself. Van Beneden and Windischmann inclined, as pre-
viously stated (p. 236), to the same opinion.
Lovén (48, pp. 5385-539), on the other hand, expressed, with some
reserve, the opinion, that in lamellibranchs it was the germinative dot
which, after rupture of the vesicle, became expelled. Leydig (49,
p. 125) conjectured the same to be true for Piscicola, and Bischoff (42,
pp. 54, 146) held to the idea that the globules observed by him in the
rabbit were at least derived from the germinative dot.
More recently Flemming (’74, pp. 278, 279) has maintained that it is
neither vesicle nor dot, but a product of the metamorphosis of both,
and believed them to be the Purkinjean vesicle. They were observed in the case of
Aplysia by P. J. van Beneden (40, pp. 242, 243, 245) who called them ‘‘ vésicules
blanches,” and in the same paper mentions their occurrence in Limax, although the
first account of their formation in Limax was that given by Van Beneden and Win-
dischmann (’41, pp. 20, 21) in the year following. .
Fr. Miller (48, p. 3) attributed to these bodies an importance in determining the
position of the planes of segmentation, and hence gave them the current German
name ‘‘ Richtungsblaschen.”
Robin ( 'G62¢ p- 150), also recognizing their constant relation to the early segmen-
tation planes, calls them ‘‘ globules polaire,” but believes that they are derived, not
from the germinative vesicle or germinative dot, but from an accumulation of clear
yolk at one pole of the egg, and that granular portions of the yolk may secondarily
make their way into the globules while the latter are in process of formation. Sev-
eral observers have alluded to the name polar globules as though it were first used by
(the elder ?) Van Beneden. I have not succeeded in finding the use of that expression
in the earlier writings of P. J. van Beneden, and am therefore of the opinion that
Robin was the first to make use of this term.
P. S. — Fol (79, p. 146 or p. 58 of separate) casts doubt on the nature of the ob-
servations made by Carus and Dumortier. He says they are currently, in his opinion
wrongly, believed to have discovered the polar globules. ‘It has been impossible
for me,” he adds, ‘‘to find in the works of these authors the description of corpuscles
which are referable with probability to the polar globules.”
I have likewise been unable to find any description in Carus referable to polar glob-
ules, unless the allusion (Joc. cit., p. 53) to ‘‘hellere durchscheinende Stellen (a, bij
which one distinguishes “an zwei polar entgegengesetzen Punkten” may refer to phe-
nomena which in some cases accompany the formation of polar globules; namely, the
accumulation of clear protoplasm at the vegetative as well as animal pole of the egg.
The protuberance outlined in the figure (IV. 4. a.) above referred to represents too
closely a nearly completed polar globule to permit assigning any other significa-
tion to it, although it may count for little, that, among many projections from the
surface of the embryo Carus has chanced to figure, without understanding its meal
ing, one of those structures over which there has been so much discussion. — With
See ee
MUSEUM OF COMPARATIVE ZOOLOGY. 391
which is expelled in the case of the acephalous mollusks. His opinion,
although subsequently substantiated, was not based on a satisfactory
knowledge of the exact nature and sequence of events in the supposed
metamorphosis.
What relation, if any, exists between the disappearance of the germi-
native vesicle and fecundation? or, granting the derivation of the polar
globules from the germinative vesicle, what is the relation between fe-
cundation and the formation of polar globules ? .
Many excellent observers have raised these questions without being
able to arrive at a definite conclusion. Thus Lovén (’48, p. 535) is un-
certain, in the case of Modiolaria, whether the migration of the vesicle to
the surface of the yolk and the dissolution of its membrane are processes
which pertain to the life of the egg or to the development engendered by
regard to Dumortier (37, pp. 10, 11, 15, Pl. I.) the case seems much clearer. Six
hours after the egg is deposited ‘‘on remarque sur le cote un hile muqueux et
diaphane (Fig. 1, X. a) qui est la véesicule de Purkinje.” Notwithstanding the erro-
neous notion of the ultimate fate of this ‘‘ hile muqueux,” I think there is not only a
probability, but almost a certainty, that it is the polar globule. The recent deposit
of the egg is in itself, perhaps, enough to make this interpretation probable, especially
in connection with the statement that the egg is at this time always totally round and
opaque ; but there is additional evidence in the further description given by Dumor-
tier. In his account of the egg on the second day he says: ‘‘ Le hile de son cété
s'est prolongé et parait formé de deux globules diaphanes, qui ne tardent pas a se
séparer et & se détacher l’un de I’autre (Fig. 2, O. a. b)..... Toutefois le hile dis-
paraissant complétement le 4° jour pour ne reparaitre que le 8° jour.”’ So far as I know,
there is only one phenomenon beside the formation of the polar globules to which
this description could possibly apply ; viz. the elimination of drops of an entirely
transparent fluid previously accumulated between the segmentation spheres. There
is little probability that these descriptions are applicable to the latter process. In
the first stage the complete rotundity and the opacity of the yolk make it improbable
that the first segmentation had been completed ; for (although the first two segmen-
tation spheres become mutually flattened so as to give the whole approximately the
spherical form again) the accumulation of the liquid would have led the observer to
qualify his assertion that the yolk was opaque ; but if the first segmentation had not
taken place, then the hilum could not have been due to the accumulated liquid, — at
least, I am not aware that any one has observed such accumulations previous to the
mutual flattening which follows the first cleavage. In the second stage the descrip-
tion and figures (Figs. 2 B, 2 C, 3 B) of two transparent globules, which do not
disappear till the fourth day, can certainly have nothing whatever to do with the
elimination of drops of clear fluid, which Dumortier himself saw and subsequently
very well described (see p. 15, and description of Fig. 8 B, p. 44) as ‘‘une goutelette
de liquide qui s’étendit bientdt dans l’albumen comme une goutte de lait qui tombe
dans leau.” Since, then, these descriptions do not relate to this elimination of
liquid, I think it will be difficult, if indeed possible, to find any better interpretation
than the one which they have for many years enjoyed.
392 BULLETIN OF THE
fecundation. De Quatrefages (48) indicates very clearly that the ger-
minative vesicle disappears in wnfecundated eggs (p. 171) of Hermella,
but also that the “clear space”? which occupies the yolk previously to
the elimination of the “globule transparent” (polar globule) in eggs
already fertilized is no longer visible after the formation of that globule.
He is uncertain whether the disappearance of the germinative vesicle is
accomplished in the same manner*in both cases. Although he thinks
Bischoff speaks too positively in saying that there is no definite relation
between the time of the vesicle’s dissolution and either the escape of the
egg from the ovary or the act of fecundation (pp. 173, 174), still he ulti-
mately (p. 181) leaves this question in an undecided condition.
Other observers have answered with sufficient positiveness, but their
conclusions have differed widely. While in the opinion of many the dis-
appearance of the vesicle followed fecundation as its immediate result,
others have as positively denied such a causal relation.
Already in 1827 Von Baer maintained that the migration and disap-
pearance of the germinative vesicle was a phenomenon of the ripening
of the egg,* an opinion which he has since taken occasion to reiterate.
(See Von Baer ’35, pp. 4, 9, and ’37, pp. 28, 157, 297.) The same con-
clusions have been reached by many other observers upon all classes of
animals.
Reichert, on the contrary (46, pp. 199, 205), evidently looks upon the
disappearance of the vesicle as the first result of impregnation in the
case of Strongylus, and Krohn (’49, p. 5, foot-note) dissents from Derbés’s
opinion (47, p. 83), when the latter makes the germinative vesicle (sphere
moyenne) in Echinus disappear before fecundation, and ascribes the sup-
posed error to want of careful study. Krohn himself observes the absence
of the vesicle and dot half an hour after fecundation (p. 7).
In 1853 Leuckart (’53, pp. 921, 922) thus summarized earlier opin-
ions: “As a rule the disappearance of the germinative vesicle is consid-
ered as the immediate result of fecundation.” But, on the strength of
the evidence before him, he did not hesitate to draw this conclusion : “If
we put all these facts together, then it really can hardly remain longer
doubtful, that the disappearance of the germinative vesicle characterizes
a process which belongs more to the formative history of the egg than
to the history of the development of the subsequent embryo.” There
are, nevertheless, many who have still insisted on the essential impor:
* “*Vesiculam Purkinji partem ovi efficacem esse credo, qua facultas feminina vim
exerceat, ut facultas masculina semini inest virili. Vesicule igitur protusio et disso-
lutio ab ovi maturitate et forsan irritatione penderent.” (Von Baer ’27, p. 29.)
)
MUSEUM OF COMPARATIVE ZOOLOGY. 393
tance of fecundation for effecting the changes referred to. Among these
may be mentioned A. Miiller (64), Haeckel ("74, pp. 141 —143), and
Biitschli (76, pp. 388, 389), who so recently as 1876 makes this sweep-
ing assertion: “ Diese Frage nach dem Austritt des Keimblischens vor
oder nach*der Befruchtung ist jedenfalls der Miihe werth, naher erortert
za werden, denn es stimmen alle vertrauenswiirdigen Untersuchungen
an wirbellosen Thieren darin tberein, dass die Ausstossung erst nach
der Befruchtung stattfindet.” But with more recent discoveries this
question seems to have come nearer a final solution in agreement with
Leuckart’s conclusion.
The reviews which follow cover only comparatively recent observations,
— principally such as have a bearing on the metamorphosis of the ger-
minative vesicle and the formation of the polar globules.
According to RatzeL unD WarscHawsky (’69, pp. 548, 549, Taf. XLI.
Figs. 1, 2) the development of the fecundated egg of Lumbricus agricola
begins with a change in the germinative vesicle, which surrenders its
sharp outline and becomes a ‘stark lichtbrechender, unregelmassig
strahliger Fleck etwas excentrisch gelegen,” and with the formation of
a narrow, clear streak in the middle of the egg underneath the altered
vesicle. This streak subsequently increases in length. Later, both
structures disappear. That which entitles these observations to a notice
in this connection is the clear streak which remained to the observers
of doubtful signification. In my opinion they saw in this streak, how-
ever ilfcompletely, the maturation spindle in process of formation out of
the germinative vesicle. I believe this view is supported by the observed
lengthening of the streak, which has so often been seen to take place with
the spindle figure. Were it not for the absence of polar globules, which
are figured only in later stages (loc. cit., Figs. 3-5), I should consider
this as probably the first cleavage spindle, since I have seen the same
relative position of the pronuclei to the spindle in the case of Limax.
The failure to connect this figure, or the germinative vesicle in any way,
with the production of polar globules, cannot be surprising, as the
authors do not seem to have bestowed any attention on the production
of what they, with Rathke, held to be only meaningless, squeezed-out
portions of the yolk.
Those eggs which do not develop retain the germinative vesicle, but
its contour becomes less distinct.
Ratzen (69, p. 565, Taf. XLII. Fig. 5) saw more than any of his
predecessors. He says: In the eggs of Tubifex, which are mature and
ready for deposit, the germinative vesicle surrenders its spherical form
4
394 BULLETIN OF THE
and sharp membranous limitation from the yolk, which it hitherto pos-
sessed, and becomes an elongated body. Its coherence and elasticity
make it possible by gentle pressure to remove it from-the yolk without
changing its form or size. In regard to its composition, it presents a
peculiar appearance. Its middle portion is, in comparison with its poles,
swollen, and exhibits a meridional striation, which results from the pres-
ence of a membranous envelope. Inasmuch as the remaining [polar]
portions of this modified germinative vesicle present no trace of a mem-
brane, and inasmuch as the median swollen portion agrees very well in
size with the [unaltered] germinative vesicle, the whole structure may
be considered as having arisen by the accumulation of protoplasm at
two opposite poles of the vesicle. The germinative spot had already
disappeared.
The expression “ meridionale Streifung” might lead one to suppose
that an equivalent of the spindle fibres had been observed, were it not
that the “Streifung” shown in the figure (Fig. 5) thas a direction at
right angles to the axis of the supposed spindle figure. Although no
stellar structures are indicated, I think one must conclude that the
figure represents an early stage in the formation of the amphiaster,
whose rays may easily have escaped detection. Whether the centres of
the hypothetical asters are to be imagined as occupying the centre of the
clear areas, or whether they correspond to the extreme points of the
figure, cannot be definitely concluded. That the astral centres may lie
at considerable distance from the periphery of the nucleus, has been
sufficiently insisted upon already in the detailed account of Limax.
The folding of the membrane, to which is due the striate appearance,
entirely precludes the interpretation of the central mass as an oblique
view of the nuclear disk. Polar globules are not mentioned.
Afterwards Rarzst (69°, p. 282) endeavors to correct the observa-
tions made by himself and Warschawsky on Lumbricus, as far as
regards the disappearance of the germinative vesicle, which he now
maintains gives rise by its deviszon to a number of clear spots.
As I have briefly stated before, OntLacHER (72 and "72>, pp. 406-410)
has described the process by which the germinative vesicle is eliminated
from the egg in the case of the trout, and also in that of the hen. (See
also Oellacher 70.) By the contractions of the protoplasm of the germ,
the vesicle is forced to the free surface, where it becomes ruptured, and,
in the case of the trout, its thick wall is spread out on the surface of
the germ as a flat, round veil. The contents of the vesicle thus set
free appear in the form of one or two finely granular spherules on the
MUSEUM OF COMPARATIVE ZOOLOGY. 395
outer surface of the germ. What becomes of them is not known with
certainty, though numerous small granules scattered between the sev-
mentation spheres at a later stage are thought to have possibly resulted
from them.
A nucleus was only once seen in the germ before segmentation, and
then not carefully studied. He thinks it certainly had no connection
with the germinative vesicle, the latter having been already eliminated.
Much of the value of Oellacher’s work is due to his employing the sec-
tion method with the objects studied. The streaked appearance of the
germ as portrayed for two sections (72°, Figs. 27, 28) is of interest as
suggesting the persistence of nuclear matter in the germ, and as possibly
showing a gyratory tendency in its substance (Fig. 28) not unlike that
seen in Limax.
Kiernenserc (72, pp. 42, 46, 47), in his well-known paper on
Hydra, describes to some extent the regressive metamorphosis of the
germinative vesicle, which occurs long before fecundation. The germi-
native dot first becomes disintegrated and dissolved. The vesicle is
forced to the external pole of the egg, where it undergoes a fatty degen-
eration and finally disappears altogether. A contraction of the vitellus
takes place soon after the disappearance of the germinative vesicle, and
is uniformly accompanied by the elimination of a few particles of the
egg substance, which the author identifies with the polar globules* of
other animals. No genetic connection between vesicle and polar glob-
ules was discovered.
Ray Lanxester (’73, p. 85) affirms for Aplysia, that “the germinal
vesicle escapes previously to yolk cleavage as the ‘ Richtungsblaschen.’”
Notwithstanding his valuable contribution to an intimate knowledge
of the nuclear changes during cell division, I think we are justified in
presuming that ScHNEIDER (73 p. 113) has overlooked some of the
phenomena accompanying the earliest changes of the egg. Biitschli
(76, p. 399) with reason questions the propriety of his calling the
nucleus of a fecundated egg the germinative vesicle. In this particular
case it would seem as though the egg represented by Schneider in Fig.
5. a, Taf. V. embraced still the germinative vesicle, containing, as the
* The criticism of Biitschli ("76, p. 384), that the existence of a ‘‘ Pseudozelle
(Dotterkern)” in these particles makes it more than probable that they have nothing
to do with polar globules, would now be without weight, for it was made at a
time when the cell nature of these structures was not understood. The probability
that these are polar globules receives also a certain amount of confirmation in the
recent studies of Korotneff ("76) on Lucernaria, a review of which is given far-
ther on.
396 BULLETIN OF THE
latter does, a single nucleolus with a minute fluid-filled space. The
most natural explanation of the case would then be, that the spermato-
zoa observed and figured within the yolk had not led, up to the time
of observation, to a real fecundation;* that the description of the
metamorphosis of the ‘‘ germinative vesicle,” as elsewhere (p. 278) given
an extenso, relates to that vesicle rather than any other nuclear struc-
ture; but that the author overlooked the formation of polar globules,
and assumed that the condition of every unsegmented egg found to
present some stage of the rosette figure must have resulted ¢mmediately
from the metamorphosis of the germinative vesicle, rather than through
the intervention of any other nuclear body.
The changes of the “ germinative vesicle” of the fecundated egg de-
scribed by Fou (’73) for Geryonia have been given elsewhere (p. 279),
since they relate to the nucleus of the first cleavage-sphere, not to the
germinative vesicle. The metamorphosis of the latter escaped him. The
“ Faltenstern ” of the egg membrane is supposed by the author to indi-
cate the spot where fecundation takes place; but I think it is more
likely that it is connected with the formation of polar globules, of which
the author usually saw one.t What that intimate relation is which the
polar globule in other ccelenterates sustains to the act of fecundation,
the author does not say. One is inclined to believe that he looked
for an orifice + owt of which the polar globule had come, and through
which the spermatozoa had penetrated znto the egg.
BaLBiaNI ('73, p. 84) denies that there exists in spiders any connection
between the nuclei of the blastoderm cells and the Purkinjean vesicle. He
adds nothing to our knowledge of the metamorphosis of this structure.
Burscuui ('73%, p. 101, Taf. XXVI. Fig. 614, 1. —1v.} unquestionably
saw and figured what is now known as the female pronucleus, but was
unable to give positive information concerning its origin. It makes its
appearance as a clear vesicle, at the pole of the egg which is directed
toward the vagina, some time after the germinative vesicle has ceased to
be visible. Whether the latter is ejected, or simply has become
* The observation of unaltered spermatozoa within the yolk gives reason to sus-
pect that the egg here figured was not capable of normal development.
+ ‘‘Vermuthlich entspricht der Faltenstern der Stelle wo die Befruchtung stattfand.
Hier befindet sich in der Hiille fast constant ein Korn oder Richtungskérperchen
von 15-20 Grésse. Ein ahnliches Kérperchen, welches mit dem Befruchtungsacte
in niherer Beziehung zu stehen scheint, habe ich auch bei anderen Coelenteraten
beobachtet.” (p. 475.)
+ “Eine Oeffnung ist beim befructeten Ei hier [i. e. at the Faltenstern] nicht 7
entdecken.”’
MUSEUM OF COMPARATIVE ZOOLOGY. Blvd
obscured, Biitschli is unable to say, but evidently inclines to the latter
opinion.
ScHENK (73, p. 369, Fig. 4) points out the existence of a small cavity
in the fecundated eggs of Raja quadrimaculata, which has a triangular
outline and opens by a narrow orifice at the surface of the formative
yolk. ‘It occupies the place of the germinative vesicle.
Vittot (74, pp. 201, 202) informs us that the germinative vesicle
has apparently disappeared in the eggs of Gordius at the time of
deposit, but the subsequent contractions of the vitellus bring into view
a nuclear structure, which he insists is the original vesicle. In his
figures (Pl. VII.) he represents only a single polar globule, but says in
the text that segmentation is preceded and accompanied (!), as in most
animals, by the formation of polar globules, the number, form, and
volume of which are variable.
In his first studies on Anodonta, FLtemMine (’74, pp. 274-279, Taf.
XVI. Figs. 10, 11, 16) traced the appearance of polar globules, but was
in doubt as to whether the second of the two bodies resulted from a di-
vision of the first one, or was separately eliminated from the yolk. The
globules are expelled from the yolk at the pole diametrically opposite the
micropyle, and the process is introduced by the appearance of a hyaline
margin which in some cases is raised to a knoblike form. This is fol-
lowed by the pushing out of a rodlike projection having a conical apex.
The formation of the first polar globule is of considerable interest,
inasmuch as its production is accompanied by the appearance of short
pseudopoda-like projections about the apex of the conical mass. This
observation stands without a parallel. The projections, although resem-
bling pseudopodia, were never observed to execute rapid motions.
A layer of granules in the middle or under the apex of the projecting
body is doubtless to be referred to the elements of the external half
of the nuclear plate. (Compare spl, Figs. 50, 40, and 67 of Limax.)
The yolk was observed to change its form periodically, during this pro-
cess of elimination, from a spherical to a more flattened condition, and
back again. At this time none of the yolks possessed a nucleus, but. in-
stead a “clear place” was to be seen (especially if the egg were subjected
to pressure sufficient to flatten it) which was not sharply limited from
the rest of the vitellus ; it simply contained fewer and smaller granules
than the surrounding yolk; it lay somewhat eccentric, nearer the pole
where the globules were eliminated.
The polar globules persist only a short time (till the fourth segmenta-
tion) ; they stain more intensely than the yolk, and in this Flemming
398 BULLETIN OF THE
finds reason for the belief that they take their origin from the nuclear
structure, — the metamorphosed germinative vesicle and germinative
dot. The second polar globule, however, cannot correspond to the whole
of the clear space noticed after the formation of the first globule. In
this he is unquestionably right, as the clear space, it will not now be
doubted, corresponds to that portion of the first archiamphiaster which
is not eliminated with the first-formed globule.
The statement by Dreck (74, p. 512) that he has recognized the: ola
globules in the case of decapod crustaceans (Maja and Carcinus) is ren-
dered comparatively unimportant by the inaccuracy of his ideas concern-
ing the nature of those bodies. According to this author the elimination
of polar globules — whose discovery he wrongly ascribes to Johannes
Miiller — is to be followed in the nemertean Cephalothrix from the first
cleavage onward. They are at first large, but afterwards become smaller,
in keeping with the diminution in the size of the segmentation spheres.
At length they fill a great part of the space between the embryo and the
chorion. This confusion of the production of polar globules with abnor-
mal processes has already been pointed out by Biitschli. Dieck, however,
observed around the germinative vesicle, and around nuclei generally, a
clear zone, and during the reappearance of nuclei after each cell division
he mentions that it is in this zone that the new nuclei make their ap-
pearance. The “zone” probably corresponds to an aster.
The unfortunate confusion which LANKEsTER (74, pp. 375, 376, Pl.
XVI. Figs. 1-7) experienced regarding the gastrula invagination of
Lymneus was due, in part at least, to not carefully distinguishing be-
tween the polar globules and the fluid excretions which are so noticeable
a feature of the segmentation stages of pulmonates.*
In a preliminary note Fou (’74, p. xxxiii.) makes brief mention of the
* He says: “They [Richtungsblaschen] may serve a useful purpose for the embry-
ologist if they enable him to recognize at any subsequent period when they are pres-
ent the original pole at which they made their appearance. But it must be borne in
mind that such droplets of albuminous matter are occasionally extruded from eggs of
the same character as those of Lymnzus at other points during later stages in the
process of segmentation of the egg sphere.”’ I believe there can be little doubt that
Lankester’s errors lay in considering the smooth rounded surface shown in his Fig. 4
to be the nutritive or less active pole of the egg, and in admitting the possibility of an
inconstancy in the relative position of the polar globules in the case of different mol-
lusks. Having often seen corresponding stages in Limax, I am convinced that the
active pole of the egg is uppermost in his Fig. 4, as well as in Fig. 7, and that his four
‘large spheres” appear large only because they are very much flattened by the accu-
mulation of fluid within. With this explanation there is no serious difficulty in un-
derstanding the process of invagination.
————or er -S
OE
MUSEUM OF COMPARATIVE ZOOLOGY. 399
changes in the Pteropod egg. ‘At the moment of deposit one only sees
in the midst of the protoplasm two molecular stars.” After the escape
of the polar globules, there appears a nuclear structure (which Fol still
insists upon calling a germinative vesicle), which in turn soon disappears,
giving place to two molecular stars. This is the beginning of the seg-
mentation, as already described for Geryonia. ‘I would only add,” he
says, “that I have seen these stars arise in the interior of the germina-
tive vesicle, an instant before its diappearance.”
The first change in the germinative vesicle of fertilized eggs of Serpula
uncinata consists, according to ScHEeNK (’74°, pp. 291 — 294, Figs. 3-8),
in its becoming notched. This change is effected by a motion in the
granular protoplasm of the yolk, which is directed, as larger and smaller
processes, toward the centre of the vesicle. During many passive altera-
tions of form the vesicle becomes smaller, and at length reaches the sur-
face of the yolk. Here it is for a time distinguishable as a clear space,
but finally this fades away till no recognizable trace of it is left. Mean-
while the germinative dot is eliminated, and lies between the yolk and
its envelope, the latter being raised into a corresponding prominence.
This eliminated dot, which is plainly stained in carmine, becomes flat-
tened against the yolk, and finally ceases to be visible, the envelope
assuming its full circular outline. The changes of the vesicle, but not
the elimination of the dot, were also seen in unfecundated eggs.
Schenk adds, that one cannot be easily induced to maintain for this
structure such a 7é/e as Robin ascribes to his polar globules, since in this
case the fate of the germinative dot cannot be further followed, and that
he has been unable to observe polar eee either in the case of Ser-
pula or Phallusia intestinalis.
A sudden contraction of the yolk follows, and afterwards it again fills
the membrane completely. The appearance of a stellate figure follows,
as described at page 283.
Although principally occupied with the events which succeed matura-
tion, AUERBACH has contributed much to the understanding of this sub-
ject, for he, more than any one else, has fixed the attention of embryolo-
gists upon the nature and origin of the first cleavage nucleus, — upon
the existence of two nuclear structures which, with Ed. van Beneden,
I have designated “pronuclei.” Auerbach (74, pp. 195 et seq., Figs.
1-7) begins the account of his studies on Ascaris and Strongylus with
a stage which follows very promptly on the fecundation of the egg. By
this epoch of fecundation, however, we are simply to understand a point
of time at which the spermatozoa are supposed to come in contact with
400 BULLETIN OF THE
the yolk, and he evidently considers the disappearance of the germina-
tive vesicle * as a criterion of that event.
Besides the entire absence of the germinative vesicle, not the least
trace of which could by any means be made visible, this stage is charac-
terized by a temporary recession of the yolk granules from the periphery
of the egg, during which the vitelline membrane is gradually formed,
probably by a condensation of a superfical layer of the protoplasm. The
return of the granules to the periphery is immediately followed by the
contraction of the whole yolk and the contemporaneous exudation of a
quantity of clear iqguor ovi. Thus is completed the formation of the first
cleavage sphere, which is throughout homogeneous.
As regards the formation of a nucleus in this first segmentation sphere,
Auerbach rejected the idea that it appears either as an entirely new
centrally located structure, or as a metamorphosed persisting germinative
* In the eggs of both these nematodes there is a slight deviation from the truly
oval outline ; one end is slightly more obtuse than the other. The more pointed end
is characterized, according to Auerbach, by several other peculiarities. It is the one
which is in advance as the egg passes through the oviduct, and therefore that which
is first exposed to the spermatozoa, probably also the part into which the spermatozoa
penetrate. Perhaps this accounts for certain advantages which the narrow seems to
possess over the more obtuse end. It is at the former that the polar globules are
found ; of the two spheres which result from the first segmentation the more volumi-
nous occupies the narrower end ; in its changes this anterior sphere slightly anticipates
the hinder one, and is subject to fewer variations from the norm ; and finally, it is
this portion of the egg from which the anterior part of the worm is produced.
Unfortunately, Auerbach has given no account of the place and manner in which
the polar globules are eliminated from the yolk. If their constant appearance at the
smaller pole of the egg could be taken as evidence that they were eliminated at that
pole, — an assumption which has a certain amount of support in the less granular
condition of that end of the yolk (see Fig. 27, Joc. cit.), and in the fact that both pro-
nuclei arise at the poles of the vitellus, —then the observation would command par-
ticular attention as showing that the almost universal relation of polar globule and first
cleavage plane is not in this case maintained.
The appearance of the pronuclei at opposite poles of the egg is not easily reconciled
with Auerbach’s ideas, for the female pronucleus, we must now assume, makes its ap-
pearance near the point where the polar globule arises, and the male pronucleus at
the large end of the egg could hardly have arisen from the influence of a spermatozoon
penetrating at the smaller. In view of the fact that Biitschli (75, pp. 208, 204) finds
the polar globule in non-parasitic nematodes usually at the equator, though sometimes
nearer the vaginal pole, and that he has observed its transportation from the place of
its origin to the smaller (vaginal) pole, it is perhaps safe to infer that Ascaris and
Strongylus offer no exception to the rule that the polar globule makes its appearance
in the plane of the future first segmentation, in which event a sub-polar position of
the globule would probably correspond to the cases of oblique segmentation so fre-
quently observed in the nematodes.
MUSEUM OF COMPARATIVE ZOOLOGY. 401
vesicle. He traced its origin from the union of two nuclear structures,
which make their appearance at the opposite poles of the egg, and, after
attaining their characteristic features, migrate to its centre.
After the egg has remained some time in a homogeneous condition,
these two structures simultaneously make their appearance as small clear
spots close under the surface at each pole. As no difference is recog-
nized between them, the further account is the same for both. At first
irregular in shape, this spot gradually enlarges and at the same time
becomes more nearly circular in outline, until, in the course of half an
hour, it has attained its full size and spherical form. It is homogeneous
and less refractive than the surrounding protoplasm, from which, although
sharply marked off, it is not separated by a membrane. It is a cavity in
the protoplasm filled with a substance probably fluid, as may be fairly
inferred from the rapid motion of the nucleoli observed later in its his-
tory. After a little time there appear within this homogeneous struc-
ture from one to five nucleoli, the size of which is generally inversely
proportional to their number. Just how they arise Auerbach is unable to
say. At first faint, they become darker, and then larger. If numerous,
they do not all appear at once, but one after the otlier in intervals vary-
ing from half a minute to a few minutes, and at points remote from each
other.
These two thus fully formed nuclear structures now begin a slow mi-
gratory motion toward the centre of the cell, where they finally meet.
Meanwhile they suffer no change of form, but the nucleoli within them
often exhibit comparatively rapid changes of position. The migration is
gradually accelerated. Hach nucleus leaves in its “ wake ” an indication
of the course it has pursued, in that the region traversed is less granular
than neighboring portions of the protoplasm. The cause of the motion
of the nucleoli the author is unable to explain.* The migration of the nu-
elei cannot have its cause in any power of motion inhering in the nucleus
itself, nor are centres of attraction discoverable ; in fact, any explanation
which presumes the protoplasm to be passive can hardly be accepted,
since its passive resistance to the motion of the nucleus would cause the
latter to become flattened in the direction of the motion. In short, it is
the contractile power of the protoplasm which forces onward the passive
nucleus, and the clear “ wake” is rather the cause than the effect of this
migratory operation. The activity of the protoplasm also finds expres-
* Subsequently (p. 247), he ventures the suggestion that it may be due (in case
the nuclei increase in size during their migration) to fine streams of fluid (Saftstrém-
chen) which must make their way from the protoplasm into the nuclear cavity.
VOL. VI.— No. 12. 26
402 BULLETIN OF THE
sion during this period of migration in the irregular changes of form
which the outline of the yolk undergoes.
Assuming that in Auerbach’s observations the female pronucleus is the
one making its appearance at the small end of the egg, an occasional
variation from the normal method is observable ; for this (female?) pro-
nucleus sometimes begins its migration before the male, and therefore
meets it between the centre and the blunter pole of the egg. Another
variation consists in the occasionally observed origin of the pronuclei at
some distance from either pole, in this case, however, usually at diametri-
cally opposite points of the surface.
The further history of the female pronucleus will be considered under
the head of Fecundation.
Van Bamsexke (’76, p. 4) has observed that in unfecundated eggs of
Tinca vulgaris a spherical portion is sometimes detached during the
active changes of form which the germ undergoes, and questions if these
are polar globules.
The fecundated Pteropod egg, according to Fou (’'75, p. 196), is desti-
tute of both membrane and nucleus. It is composed of two parts, for-
mative and nutritive, the latter being a network of protoplasm in whose
meshes are found nutritive globules. At the centre of the formative part
there is a star formed by granules of protoplasm arranged in straight di-
vergent lines which extend as far as the limit of the formative part ; the
nutritive globules also arrange themselves in lines. After the escape of
the polar globules a nucleus appears at the centre (au centre) of the star.
The latter. disappears in proportion to the increase in the size of the nu-
cleus ; and the granules and globules cease to be in line.
In his second paper on the development of Anodonta, FLemmine (75,
pp. 109-118) makes some additions to his previous communications on
the earliest changes of the egg. The clear spot in the yolk, although
less distinct, is visible after the elimination of the polar bodies is com-
pleted ; it therefore cannot have corresponded to the second polar globule
alone. The latter, at first naked, possesses, after a variable length of
time, a membrane. The appearance within it of a large, usually rough,
angular, and highly refractive corpuscle, generally attached somewhere
to the membrane, is probably a symptom of the death of the globules.
The corpuscle and membrane stain more intensely than the contents,
“so that one is reminded of a small cell with nucleus, or a nucleus with
nucleolus. It would of course in the diagnosis be premature to decide
by such a similarity.” The polar globules are found to persist, in @
shrivelled condition, much longer than was at first supposed.
MUSEUM OF COMPARATIVE ZOOLOGY. 4038
As Oellacher made considerable advance on his predecessors, owing
largely to the use of sections, so Flemming certainly followed rational
methods in watching closely the results of staining, and by this means
he came near anticipating the later discoveries of Hertwig. As the re-
sult of his own observations and those of Oellacher, Flemming insists
upon a fundamental importance for the polar globules, principally on
account of their constancy and their reaction with staining fluids. Of
the manner in which they arise, he still leaves us in doubt. Flemming’s
principal objection to considering them the eliminated germinative vesi-
cle had been the discovery, at a little later stage, when the radial figures
preceding the first cleavage have already appeared (loc. czt., Taf. III.
Fig. 2), of a small, deeply staining body (nuclear disk of first segmenta-
tion sphere) in the middle of the yolk. Since Fol has deduced a similar
nuclear remnant directly from the old nucleus of the egg (germinative
vesicle), it is hard to understand, he says, how almost the whole of it
(germinative vesicle) should have been eliminated. Auerbach’s discov-
eries, however, now come to the rescue, and this “remnant of a nucleus”
(Fol) may be supposed to descend from the secondary nucleus (nucleus
of the first cleavage sphere), thus leaving no objection to a total elimina-
tion of the germinative vesicle. Influenced by the prevailing dogma
that the formation of the polar globules is essentially a process of elimi-
nation, perhaps a necessary elimination, Flemming naturally raises the
question if such does not precede each act of proliferation, — especially
since the morphological extinction of the nucleus precedes every division
of a segmentation cell, — and, in the absence of any evidence of the elimi-
nation of polar globules or their like during segmentation, answers it
only by declaring that “ nothing compels the assumption that every pro-
cess which characterizes the beginning of the construction of a body
must accompany each individual phase of its advance.”
The preliminary account given by Butscutr (’'75, pp. 203, 208-210)
from studies on several nematodes and two pulmonate mollusks — Lym-
neus and Succinea — embraces a valuable contribution toward deter-
mining the fate of the germinative vesicle and the origin of.the polar
globules. Soon after the eggs of non-parasitic nematodes enter the
uterus, the germinative vesicle, having lost its dot, becomes less distinct,
and approaches the surface of the yolk, usually at the equator, but some-
times nearer the vaginal pole. The surface of the yolk here becomes
depressed to receive the clear mass of the vesicle, which lies, as it were,
sunk in a pit of the granular yolk. In the case of Tylenchus, as the
vesicle reaches the surface a small, round, rather dark body is pushed
404 BULLETIN OF THE
out, apparently from the germinative vesicle, and it agrees very closely
in appearance with the germinative dot. It is the polar globule. The
vesicle appears to sink back into the yolk. In Cephalobus (Anguillula) —
the germinative vesicle probably spréads out its substance either zz. or on
the clear protoplasm which at this time forms the outer layer of the
yolk. Hereby, it is presumable, the nuclear substance subsequently ac-
quires a closer relation to the spermatozoon still attached to the surface
of the yolk. After the polar globules appear, they are often shoved toward
the vaginal or smaller pole of the egg. | .
The eggs of Cucullanus are of the greatest interest. Biitschli here
makes the discovery of a peculiar spindle-shaped body, which he at once
homologizes with the ‘semen capsule” of Infusoria, — a structure arising
from the so-called nucleolus. It is hard to say what structure in the fe-
cundated egg is homologous with this infusorian nucleolus; he conjectures,
however, that it is the germinative dot, and that consequently it is the
latter which gives rise to this remarkable structure. In place of the no
longer visible germinative vesicle there lies in the yolk, says Biitschli, an
elongated, portly, spindle-shaped body of exceedingly interesting constitu-
tion. It is two thirds as long as the diameter of the yolk. Its middle is
swollen, and its ends are drawn out into fine points. Its mass is darker
than the yolk, tolerably homogeneous, often somewhat brilliant, and dis-
tinctly and finely fibrous lengthwise. Each of the fibres merges at the
swollen middle part into a thick, dark, lustrous portion, which discloses a
composition out of serially arranged granules. This spindle is ejected
from the yolk, on the surface of which it is seen to lie. But what be-
comes of it he is unable to say. From a comparison with the polar glob-
ules of the snail’s eggs,* Biitschli conjectures that the two structures
(spindle and polar globules) are identical, and that the dark granules and
fibres in both cases correspond, although no intermediate stage between
the two was discovered. _ |
Concerning the origin of the new nuclei of the first segmentation sphere,
Biitschli is able to confirm in part Auerbach’s observations, but also to
add observations not directly reconcilable with his theories. The nuclei
arise in the clear protoplasm of the periphery of the egg, which is accu-
mulated at certain points. It is not to be concluded that the nucleus
is the result of the metamorphosis of the protoplasm itself, it is formed
rather from the material of the germinative vesicle. In Cephalobus rigi-
* These appear in the form of two more or less spherical bodies, connected by a
stalk, and containing each a disk of granules, the individual grains of each disk being
joined to the correspondingly situated grainsf the other by pale delicate filaments.
MUSEUM OF COMPARATIVE ZOOLOGY. 405
dus, Rhabditis dolichura, Diplogaster, and Succinea, there appear only two
such nuclear structures ; in Cephalobus, at the poles, but not always at
the same time ; in Rhabditis, one at the vaginal pole, the other at the point
of the surface where the vesicle disappeared, whether the equator or nearer
the vaginal pole. The migration and union of these two nuclei, except
in Cephalobus, is less regular than Auerbach represents it to be. The
amceboid motion of, the yolk at this time is sufficient to explain the mi-
gration, but not the coalescence, of the nuclei. In the cases of Rhabditis,
Cucullanus, and Lymneeus there are, however, more than two nuclear
structures, — from three to eight, or even more, according to the animal.
In Cucullanus these arise close under the surface at points remote from
each other ; in all cases they are at first quite small, and successively
unite till a single nucleus results. In the author’s opinion the formation
of the nucleus of the first segmentation sphere by the union of several
nuclear structures, since it is of wide-spread or general occurrence, refutes
Auerbach’s idea that the whole process results from fecundation taking
place at a definite pole of the egg, and the same is shown even more con-
clusively by the fact that the nuclei of later generations also arise from
the union of several nuclear structures.
Gorrte ("75, pp. 20-22) has described the regressive metamorphosis
of the germinative vesicle in the case of Bombinator igneus. After
approaching the upper (dark) pole of the yolk, it is found to have suf-
fered diminution of volume, so that it no longer fills completely the
cavity in the yolk which it once occupied. The remaining space of this
cavity is filled with a clear fluid. At a later stage there appears at the
centre of the dark pole, therefore directly over the vesicle, an irregular
yellow spot, which is found, on making sections, to be due to an inter-
ruption or obliteration of the pigment layer, which thus allows the un-
colored yolk to come to the surface. It is found at the same time
that the cavity about the shrunken vesicle has disappeared. Goette
| concludes that the former appearance is caused by the escape of the clear
| fluid of this cavity, whereby the integrity of the pigment layer is inter-
| rupted. There are still some traces of the germinative dots and of the
| membrane of the vesicle. A little later there is to be found in place of
| the vesicle only an exceedingly fine-granular substance without definite
limits. All this takes place before the eggs are laid, therefore indepen-
| dently of fecundation.
| In freshly laid eggs certain changes in the region of the yellow spot
“are to be observed. But only a few of the fresh eggs exhibit all the
phenomena. The middle of the spot is often depressed, and sometimes
)
}
i
406 BULLETIN OF THE
presents the same appearance as the button used to upholster a cushion.
After a short time the button disappears, and in its place there remains
a hole such as arises in making a thrust into a doughy mass. This hole
— there may be several of them — may remain till segmentation ensues,
or it may disappear earlier. The yellow spot ultimately vanishes.
Is not this “button” identical with the spheroidal structures discoy-
ered in fishes by Oellacher, and considered by him as the representatives
of the polar globules ?
Of the results attained by BUrscuii (75%, p. 430) in a second prelimi-
nary paper, I will here call attention only to the modification of his views
concerning the source of the spindle-shaped body. He now believes it
must be considered the metamorphosed nucleus rather than nucleolus,
and that in the light of this his previous conclusions are to be correspond-
ingly modified. Further details of his paper are given at page 289.
SELENKA (75, p. 444) compresses into few words his observations on
Phascolosoma elongatum. Some time after fecundation the germinative
vesicle disappears, the yolk contracts, and there is pressed out a drop of
protoplasm, which he thinks may be the remnant of the “cell nucleus,”
— perhaps excrement of the egg. I think it is without doubt a polar
globule.
Fou’s ("75", pp. 104-108, 198, Pl. I. Figs. 3, 4, Pl. VII. Fig. 2, and ~
Pl. VIII. Figs. 1-3) illustrated paper on the development of Pteropoda,
beside giving a summation of results (p. 198) in the words of his prelimi-
nary paper, furnishes additional facts of interest, and affords by the fig-
ures a better means of judging accurately the nature of his observations.
He says the centre of the delicate star which occupies the middle of
the formative part of the egg at the time the latter is laid, is not occu-
pied, as one might expect, by a corpuscle differing from the surrounding
stroma; the granules composing the star also occupy its centre. No
activity is to be attributed to the granules themselves ; they are only the
landmarks, as it were, of the intimate molecular movements of the proto-
plasm which one is unable to observe directly. Some minutes after the
egg is laid this star begins to elongate in the direction of the long axis of
the egg. It soon divides into two stars, of which one continues to occupy
the centre of the protoplasm, while the other reaches the surface in the
middle of the protoplasmic area. This point then becomes elevated as
a small nipple, and separates itself from the yolk as a spherical globule,
for which Fol adopts the term corpuscle excrété, or corpuscle de rebut,
as better reflecting than does the term “ Richtungsblischen ” its entire
want of significance in the subsequent development. This polar globule
MUSEUM OF COMPARATIVE ZOOLOGY. 407
divides into two, usually unequal portions. The escape of two globules,
one after the other, was never observed.
I think these statements about the division of the polar globules would
bear the confirmation of renewed observations.
It is the central part of the star which escapes as a polar globule, and
the interior of the globules becomes differentiated into protoplasm and
nucleus.
This last statement, like Flemming’s, appears almost to forestall the
work of O. Hertwig, but it will be observed, after all, that there is a
wide difference between the differentiation of an excreted corpuscle into
nucleus and protoplasm after it is expelled from an egg, and the process
of division by which the polar globule is really formed.
That which remains of the peripheral star, continues Fol, is little by
little mingled with the protoplasm; but the other star, which is more
extensive, always occupies the centre of the protoplasm ; z¢s centre be-
comes homogeneous, and the star gradually disappears. There arises at
the centre of this star a homogeneous corpuscle of slightly less refractive
power than its vicinage, whether a vesicle or a more or less solid body
is hard to say. Soon two or three similar structures make their appear-
ance by the side of the first, and from the fusion of all results the “ ger-
minative vesicle” or nucleus of the fecundated egg.
Fol figures only one case (Cleodora, Pl. VII. Fig. 2) in which there is
more than a single homogeneous corpuscle of this nature, and only two
are indicated there, one of which we may safely assume is the male pro-
nucleus. From a comparison with his other figures of early stages of
Cymbulia, I am almost certain that the nuclear structure (v) represented
as occupying the centre of the deeper star in Fig. 2 of his eighth plate is
not the female, but the male pronucleus, — in other words, that the aster
of which it is the centre has no such genetic connection, as Fol assumes,
with the remnant of an aster (a) lying under the polar globule. There
are several reasons why it is more consistent to assume that Fol has con-
founded these two structures, than to grant that the deep star of the figure
referred to is one which took its origin from a division of the first aster.
|Special attention had not been called to the different origin of these
| nuclear structures, even by those who had observed them ; again, I know
of no parallel case where the female pronucleus lies so much nearer the
vegetative than the animal pole of the egg; and, finally, I believe this
| assumption explains why Fol allows this nuclear structure to occupy the
centre of the stellate figure, a thing which can hardly be predicated of
. the female pronucleus and its aster before the disappearance of its rays.
|
408 BULLETIN OF THE
The main objection to this view is the fact that no other complete aster,
and no indication of another nuclear structure which might be the female
pronucleus, is made to appear in this figure. Ican only assume that the
latter was overlooked.
As the ovarian egg of Toxopneustes lividus approaches maturity it
contains, according to O. Herrwic (’75, pp. 349 — 358), a large spherical
germinative vesicle with nuclear membrane derived from the protoplasm,
clear contents, and a spherical germinative dot of constant size (13 p)
and homogeneous structure. The dot is deeply stained in carmine, the
clear contents only feebly. The two are designated as nuclear substance
and nuclear juice respectively. Besides these, a network of fine pale
fibres stretches through the vesicle, for whose membrane it forms
a lining, and is especially concentrated about the dot. In the mature
egg found in the oviduct, on the other hand, the germinative vesicle has
disappeared without leaving a trace, but there exists a small clear spot
which before was not present. The latter is spherical, and 13 w in diam-
eter. Intermediate stages lead Hertwig to the conclusion that the vesi-
cle is expelled from the egg, that it at first lies in a lenticular depression
of the yolk, but afterwards becomes flattened, that its membrane is
dissolved and its contents become disintegrated, and probably that it
is subsequently absorbed by the yolk. He believes, however, that the
_ germinative dot persists without change, and either actively or passively
comes to occupy a position in the yolk, as the clear spot already alluded to.
The assumption of the identity of the germinative dot with the clear spot
(Eikern) is supported in the author’s opinion by equality of size; and by
the facts, that both consist of a tolerably firm homogeneous substance
without enveloping membrane; that both are stained intensely in carmine
and blackened in osmic acid; that the disappearance of, or any change
in the dot, could not be observed, nor any steps in the formation of the
Kikern; that both structures are never met in the same egg, and never
are both absent; and, finally, that the Eikern first appears near the met-
amorphosed germinative vesicle, while the dot is last to be seen in imme-
diate contact with the surface of the yolk. The necessity of a migration
from the vesicle into the yolk cannot be an objection to the identity,
since nucleoli have often been observed in amceboid motion.
In a general discussion of the topic, Hertwig attempts to harmonize
conflicting views, or at least to explain the reasons of such differences.
The testimony of those who describe a regressive metamorphosis and
disappearance of the germinative vesicle must be accepted as valid for
the cases described ; the positive assertions of those who claim that the
it
|
|
|
|
{
ee ee Eee eee
MUSEUM OF COMPARATIVE ZOOLOGY. 409
vesicle divides and gives rise directly to the nuclei of the segmentation
spheres are, however, capable of another explanation, and such cases are
therefore not to be considered as exceptions to the ordinary course of
events. The trouble lies in the confounding of two entirely different
morphological structures, — the germinative vesicle and the egg nucleus
(Eikern). The former possesses a firm membrane, fluid contents, and a
compact germinative dot ; the latter is without membrane, homogeneous,
and without a nucleolus. As it is the latter which has been observed to
divide, Hertwig concludes that one may already affirm with certainty
that at the maturity of the egg the germinative vesicle as a morphological
structure perishes. 'To say how the “ Eikern” originates is more difficult.
A cardinal point is touched by the question, Does the egg exist at a
definite stage of its development as an enuclear yolk mass, —a cytode?
The evidence furnished by those who maintain that such is the case,
Hertwig endeavors to weaken, by showing that, although a germinative
vesicle could hardly be overlooked, it would be quite easy to pass unno-
ticed so small and little differentiated a structure as the germinative
dot, —the more, since anything like a satisfactory conclusion can only be
reached by having recourse to various reagents, and especially to meth-
ods of staining. His own observations have shown conclusively that in
some apparently very carefully studied cases a nuclear structure was
really present, and had been overlooked by his predecessors. Moreover,
in most cases the possibility of the persistence of the germinative dot had
not been sufficiently impressed upon the observer to make the observa-
tions certain on this point. Even in those cases (Auerbach and Stras-
burger) where a direct observation of the origin of the new nucleus is
claimed, it is not impossible that a very small germinative dot may have
remained unobserved and been in reality the initial stage of the supposed
hew structure. The evidence, then, in favor of a new origin for the
“ Hikern” is insufficient ; for, on the one hand, it is not established that
the egg passes through the cytode condition, and, on the other, the posi-
tive statements that the nucleus is a new creation are capable of another
explanation. Another error is coupled with this; namely, that fecunda-
tion is the cause of the disappearance of the germinative vesicle and of
the formation of a new nucleus. “ Der Schwund des Keimblischens und
die Entstehung des Hikerns sind vielmehr Vorgiinge, die einzig und allein
mit der Reife der Eier zusammenhiangen und die Befruchtungsfihigkeit
derselben herbeifiihren.”
Finding no entirely insurmountable obstacle in the literature, and sup-
ported by his own observations, he draws the general conclusion that “ in
410 BULLETIN OF THE
the whole animal kingdom the ‘egg nucleus’ of the mature egg capable
of being fecundated arises from the dot of the germinative vesicle which
[latter] is dissolved.” |
In a paper on the development of fresh-water pulmonates, Rast (’75,
pp. 197, 198, 223) adopts Haeckel’s view of the phylogenetic significance
of the disappearance of the germinative vesicle; namely, that it is evi-
dence that the earliest ancestors of the Gasteropoda, as of all other living
organisms, were of the simplest possible structure. The polar globules
emerge from the yolk on account of its contractions during the first seg-
mentation, and are usually two in number, the first one being the larger.
Rabl entertains peculiar ideas concerning their physiological signification. —
Since, after a period of quiet, they are uppermost, he concludes that the
pole at which they appear is the specifically lightest part of the egg, and
that it is safe to assume, inasmuch as they are thus interposed between
the egg and the envelope of the albumen, that their function is to protect
the egg from pressure. For this reason one must consider these struc-
tures protective organs of the embryo acquired through adaptation to
the method of unequal segmentation.
In Helix at the time of the disappearance of the germinative vesicle,
or soon after, there emerge from the yolk, according to Von JHErRiNG (’75, |
pp. 303, 304), from one to three polar globules. Whether the vesicle
simply perishes, or is ejected, whether or no there is a connection be-
tween it and the polar globules, cannot be determined on eggs so unfa-
vorable for study. The formation of the globules is proof for the author
_of the existence of a vitelline membrane (Taf. XVII. Fig. 2. d).
‘Without contributing any personal observations which bear immedi-
ately on the early stages of the egg, Harcken (’75, pp. 421, 426, 434,
435, 446, 480-483) utilizes the preponderating evidence in favor of
the disappearance of the germinative vesicle in support of his theory of
the palingenetic significance of the cytode stage of the egg, as a “ Riick-
schlag der einzelligen Urform in die primordiale Stammform des Mo-
neres.” If this atavistic return to the cytode condition should be
established for only a part of the animals, but fail for the remainder,
then the development in the latter cases would have to be considered as
a ceenogenetic process.
Lupwie (75, p. 210) was unable to detect any such details in the
early stages of the egg of Cheetonotus as have been described by Auer-
bach and others, and therefore was only able to say that the germina-
tive vesicle disappears entirely while the yolk undergoes contractile
changes.
MUSEUM OF COMPARATIVE ZOOLOGY. ALT
I should not have occasion to call attention here to a paper by
Semper (75, pp. 4-13), in which he discusses the origin and nature of
the so-called Testazellen of ascidians, were it not for his attempt to
identify these structures with the polar globules of other animals, — the
less occasion, as his observations relate principally to artificial produc-
tions which do not contain nuclei (although the same is true in his
opinion for the normally produced “ Testazellen’’) and are only entitled
to the name ‘‘ Testatrvopfen.” The reasons given to establish the iden-
tity alluded to have proved to be unfortunate, as Whitman (’78") has
already pointed out. Nor can Semper’s claim be maintained, that the
polar globules “first make their appearance at the moment of segmenta-
tion,” * or that they ‘‘are enuclear” ; nor is there any evidence to prove
that they are capable of moving themselves in an ameeboid fashion
around the embryo. Even though a change in the contour of these
globules has often been observed, and the existence of rigid processes
which resemble pseudopodia has been demonstrated by Flemming, it is
far from proving the polar globules endowed with the power of mak-
ing excursions on their own account about the embryo. As Kupffer
(70, pp. 123, 124, and 72, p. 366) has shown, the “ Testazellen” appear
while the germinative vesicle is still intact, and this is not objected to
by Semper, who admits that they arise, not from the nucleus, but from
the yolk. The genetic connection of the polar globules with the germi-
native vesicle therefore forbids the comparison which he has instituted.
But when Semper, partially recognizing the possibilities of such a ge-
netic relation, in a foot-note substitutes for an “ Uebereinstimmung in
fast jeder Beziehung” a physiological comparison between these two
sorts of bodies, he is no longer defending the view already promulgated,
| —a view, it is to be observed, which he endeavored to establish with
morphological arguments,—but is really supporting new ideas. The
physiological dle which Semper discovers in these bodies is ‘the de-
tachment of a hitherto integral component of the egg-cell, in some
manner a defecation of the same, an elimination of substance apparently
useless for the approaching processes.”
In a preliminary paper on early stages in the development of the
rabbit, Ep. van Benepen ('75, pp. 690 — 693, 695-700) signalizes the
| existence of two or three small round bodies (psewdo-nucléoles) and a
the polar globules in Physa arise during segmentation will also probably be found to be
inaccurate, for it is not consistent with what is known of the nature of these globules
in all other investigated animals.
H
|
/
{
| * P. S. — The recent statement by Brooks (80, p. 79, Pl. I. Figs. 3, 4) that
;
|
granular substance (nucleoplasma) in the germinative vesicle, in addition
to the nucleolus and a clear liquid. The granular substance often as-
sumes the form of a network in the growing egg. At maturity the
vesicle, instead of being central, becomes superficial, takes an ellipsoidal |
form, and then becomes more and more flattened against the zona pellu- —
cida. The vitellus is now composed of a medullary mass, and a cortical —
layer which becomes clear at the contact of the vesicle. Clear proto-
plasm is accumulated around the vesicle in the form of a biconvex
lens, —la lentille cicatriculaire, — which depresses the medulla. As
soon as the germinative vesicle comes in contact. with the zona, the
nucleolus joins the membrane of the vesicle, against which it is flattened
and with which it unites ; its plastic substance spreads out into a plate
with, at first, a median thickening, — plaque nucléolaire.
At the same time the membrane of the vesicle thins out, especially
where it is in contact with the cicatricular protoplasm. It is probable
that the substance of the membrane is attracted toward, and unites
with, the nucleolar plate. The nucleoplasm and pseudo-nucleoli give
rise to a mass of granular substance, — corps nucléoplasmique. The
liquid and limpid contents of the vesicle mixes with the cicatricular
protoplasm upon the rupture of the membrane of the germinative vesi-
cle. At the same time the nucleolar plate, by virtue of its inherent
contractility, is amassed into a body having sometimes the form of an
ellipsoid, often that of a lens; or of a calotte,— corps nucléolaire. At
the moment the germinative vesicle disappears, the directive bodies are
eliminated. There are two of these, but they are unlike both in compo-
sition and signification ; one is the nucleolar body, the other the nueleo-
plasmic body. The former is stained in picrocarminate of ammonia,
the latter is not. The cicatricular lens becomes granular, and thus
indistinguishable from the cortical layer of the yolk. With the disap-
pearance of the germinative vesicle begins the retraction of the vitellus,
which consists in the expulsion of a transparent liquide perivitellin, and
is accompanied by amceboid movements. Subsequently the vitellus
resumes its spherical form, and no division into cortex and medulla is
visible. In this cytode state the egg is entitled to Haeckel’s designa-
tion, “monerula.” All the preceding changes are independent of fecun-
dation, and are connected with the maturation of the ovum. In the
case of the rabbit they are accomplished within the ovary.
Although a portion of what is said in his chapter on the “ Formation
of the first Embryonic Nucleus’ pertains to another part of the present
review, I shall give it in this connection. Shortly after fecundation
412 BULLETIN OF THE
imi ie tt itt
MUSEUM OF COMPARATIVE ZOOLOGY. 413
the substance of the vitellus consists of three layers, — superficial, inter-
mediary, and central. The second is coarsely and irregularly granular,
and more opaque than the other two; the central is clearer, but
uniformly granular ; the superficial is almost homogeneous, very refrin-
gent, and contains only punctiform granulations. At a point of this
outer layer a thickening occurs, and in this point appears a small, round
body, which is destitute of granulations and resembles a vacuole ; but in
osmic acid this so-called vacuole darkens and assumes a gray tinge,
while the vitellus is colored brown. ‘This is the pronucleus périphérique.
This sinks deeper into the yolk, at the same time becoming larger, and
there appear within it numerous very refringent corpuscles of variable
size which resemble nucleoli. In the “central mass” of the egg there
appear simultaneously two or three small clear irregular masses, which
directly unite into a body with bunched (bosselé) surface. This occu-
pies from the first the centre of the egg. It is called by Van Beneden
pronucleus central. It differs from the peripheral pronucleus in being
considerably larger, and in having a less distinct contour. The two
approach till they touch each other at the middle of the yolk. The
peripheral pronucleus is spherical, and its contour is regular. The
central has the form of a calotte or of a flattened crescent with blunt
horns,* its concavity being moulded upon the peripheral pronucleus,
from which it is at first separated by central protoplasm sometimes
containing several voluminous and refringent granules. In most of the
eggs, however, the pronuclei touch or are separated by only an imper-
ceptible layer of vitelline protoplasm. The convex face of the central
pronucleus is sometimes regular, sometimes lobed, and occasionally
divided into two parts in such a manner that there are three conjoined
clear bodies. The substances of central and peripheral pronucleus are
optically alike, and both exhibit rounded refringent corpuscles of vari-
able size, — the nucleoli.
The peripheral pronucleus increases rapidly in size, but preserves its
spherical form. The central diminishes in volume. They become much
less apparent, and at length there exists only one nucleus formed at
the expense of the two. Whether they fuse, or one is developed at the
expense of the substance of the other, the author is unable to say. This
nucleus has an irregular form, indistinct contours, and is composed of a ,
_ homogeneous substance in which nucleoli are not distinguishable. From
the time the pronuclei approach each other in the centre, the vitellus
* These eggs were treated with 1% osmic acid, put two or three days in Miiller’s
fluid, and then mounted in glycerine.
414 BULLETIN OF THE
presents a radiated appearance, which the author does not, however, fur-
ther describe. These latter stages are exhibited by unsegmented eggs
found in company with eges already divided into two segments, taken
from the middle or from the lower half of the oviduct.
From all this it is concluded that the first embryonic nucleus is devel-
oped at the expense of two pronuclei, one peripheral, the other central.
As the spermatozoa have already been shown to become mingled with
the superficial layer of the yolk, it is probable that the peripheral nu-
cleus is formed, at least partially, at the expense of the spermatic sub-
stance. ‘If, as [ think, the central pronucleus is formed exclusively
from elements furnished by the egg, the first nucleus of the embryo will
be the result of the union of male and female elements.” This latter,
however, he expressly states, is only an hypothesis.
In the description of the polar globules there is a notable deficiency.
Although a fundamental difference is maintained for the two globules,
we are not informed of the order in which they make their appearance.
In the present state of our knowledge it can hardly be granted that there
is any such fundamental distinction between the two as Van Beneden
maintains ; it would nevertheless be interesting, and possibly not with-
out important significance, to know if in any case there is a noticeable
difference in the intensity with which these globules respond to the in-
fluence of reagents, especially of staining fluids. For Limax I can only
report, without having directed particular attention to the point during
my observations, that I have not noticed any constant difference, though
I should not wish to assert positively that a more careful study, limited
to this single point, would not teach otherwise.*
In another direction the studies of Van Beneden are of especial inter-
est. I refer to the condition of the two pronuclei, which he has described
as a moulding of the central (female) upon the peripheral pronucleus.
The possibility of this condition having been produced by the influence
of the hardening reagent (osmic acid), does not seem to have occurred
to the author. The more I reflect upon it, the more it seems to me this
condition may be attributable to the same cause as that which produces
similar conditions already described for eggs of Limax treated with the
* There are, however, some reasons why it would be difficult to reach entirely con-
vincing evidence on this point. A comparison between the first globule of one egg
and the second of another would have to deal with unknown individual differences in
the eggs, and other possible differences of conditions ; while in a comparison between
the two globules of the same egg one could not ignore the possibility of changes (of
degeneration) in the older of the two globules which would seriously diminish the
value of such comparisons.
MUSEUM OF COMPARATIVE ZOOLOGY. 415
same reagent. I will therefore state somewhat more explicitly my con-
ception of how this condition may have been brought about. The sudden
loss of a quantity of fluid would not be covered by a gradual and uniform
shrinkage of the whole nucleus, but would be followed by a giving way
of the wall at its weakest point. There is certainly considerable evidence
tending to show that that portion of either pronucleus which is directed
toward its mate is the one which first shows signs of losing its integrity
(compare Limax, I'ig. 70), —is therefore, we may assume, least capable
of withstanding external pressure. It would not be surprising, then, to
find either of the nuclei yielding first at this point. There are manifest
reasons (their close approximation) why the apposed faces would not
yield by a movement in opposite directions; the one which, from any
cause, exhibited the earlier or stronger tendency to such a change, would
entail in its action the corresponding face of its mate. The latter would
thus fill the depression caused in the surface of the former. Where the
depression in the latter nucleus to balance this out-pushing should occur,
would depend, aside from the point of least resistance, upon the direction
already given to its substance by the process just described. Thus the
pole opposite the eminence already formed would be the point to yield.
Although described as successive, these events may nevertheless be con-
ceived as simultaneous in their occurrence. Such a conception would, it
seems to me, be quite feasible in explaining the shapes presented by the
pronuclei in the case of Limax, and at the same time offer a possible ex-
planation of the apparent absence of nucleoli. In the case of the rabbit,
as described above, however, it is only the central pronucleus which thus
suffers an involution. This appears at first to offer an objection to the
above explanation, but when one reflects that the central pronucleus is
described as being much larger and less conspicuous than its mate, it is
possible to believe that this alone is enough to indicate that the central
pronucleus may lose much more fluid than does the peripheral. A more
Serious obstacle appears to lie in the fact that here the nucleoli probably
remain visible notwithstanding this condensation. Moreover, these are
not occasional but constant conditions in the approximated pronuclei of
rabbits’ eggs, so far at least as can be inferred from the description. If
I had been able to reproduce these conditions, even with other reagents
than osmic acid, I should be less confident that they represented relations
not normal for living pronuclei.
Scuuuze’s ("75°, p. 267) excellent paper on the development of Sycan-
dra, unfortunately, does not afford much insight into the changes which
overtake the germinative vesicle. He believes it disappears, but has not
seen any polar globules.
416 BULLETIN OF THE
Rosrn ('62, ’62°-7) deserves great credit for having a long time ago
called especial attention to the changes which the egg undergoes previous
to cleavage. The changes within the cell were, however, incompletely
observed, and, though still (1875) maintained, in many particulars funda-
mentally wrong. In his more recent memoir on the development of the
Hirudinea, Rosin (75, pp. 26-79) has reproduced with slight additions
these earlier papers. The description in the one on the formation of the
polar globules is of particular interest, as it contains an allusion to a phe-
nomenon occasionally seen in Limax, but not hitherto noticed in other
animals. Robin says (624, p. 156, Fig. 8, and '75, p. 35, Fig. 10), in
describing the formation of the first polar globule in Nephelis: “ At the
same time (i. e. during the constriction which rounds off the polar globule)
the clear space of the vitelline mass diminishes more and more, until the
separation is complete, 07 a plane of division is produced at the junction
of the vitellus and the part which is narrowed into the form of a pedicel.
This plane of division presents the aspect of a slender grayish or blackish
transverse line, and establishes a complete separation between the vitel-
lus and its prolongation, which then constitutes a distinct polar globule.”
Although this plane does not (in his figures) quite correspond in position
to that which in Limax I have ventured to call the cell plate, I have
little doubt that it is really the same thing. It seems also in Nephelis —
to be only an occasional method of finally terminating the direct connec-
tion of yolk and polar globule.
Robin has in his recent work (75, pp. 97-105) given a detailed ac-
count of the changes which accompany the formation of “ polar rings”
in Clepsine, or of such as can be seen on living eggs. As this does not
very essentially differ from the account given by Whitman (’78*), I omit
a review till it can be given in connection with the observations made
by Whitman on the accompanying internal changes,
The first chapter of BaLrour’s (’76, pp. 378 — 387, Pl. XV. Fig. 1, and
"78, pp. 1-9, Pl. I. Fig. 1) Development of Elasmobranch Fishes is de-
voted to the ripe ovarian ovum. Here he concludes that observations
in the case of Raja batis, as far as they go, tend to show that the thick
membrane of the germinative vesicle is expelled, but that the contents
of the vesicle become mingled with the surrounding yolk. He explains
(p. 8) how, under certain assumptions, a ‘“ consistent account of the be-
havior of the germinative vesicle throughout the animal kingdom” may
be framed. “The germinative vesicle, usually before, but sometimes im-
mediately after impregnation, undergoes atrophy, and its contents become
indistinguishable from the remainder of the egg. In those cases im
MUSEUM OF COMPARATIVE ZOOLOGY. ALT,
which its membrane is very thick and resistant, —e. g. Osseous and
Elasmobranch Fishes, Birds, etc., — this may be incapable of complete
resorption, and be extruded bodily from the egg. In the case of most
ova it is completely absorbed, though at a subsequent period it may be
extruded from the egg as the Richtungskorper. In all cases the contents
of the germinal vesicle remain in the ovum.”
In a paper on the germinative vesicle and first embryonic nucleus
Ep. vAN Benepen (764, pp. 38-76, and ’76°, pp. 153-178) gives a
very minute account of the disappearance of the vesicle in Asteracan-
thion rubens. Much of this paper is taken up with a comparison of
his results in this case and in that of the rabbit, but more especially
with a comparison of his own results and those reached by Hertwig in
the study of Toxopneustes. We learn here (76%, p. 40) for the first
time definitely, that in the rabbit the nucleoplasm with the pseudo-
nucleoli forms the second of the two polar globules. He expresses here
more positively his conviction that the substance of the central pro-
nucleus is absorbed in an endosmotic way by the peripheral pronucleus.
The vitellus of the Asteracanthion egg is composed of a clearer, less
granular cortical layer with radiated striations, and a central mass
which occupies two thirds the diameter of the egg. In the germinal
vesicle are to be distinguished the parts already described in the case of
mammals: a nuclear membrane enclosing a transparent and perfectly
homogeneous liquid ; a germinative spot formed of a very refringent
and brilliant substance enclosing a variable number of clear vacuoles ;
a reticulum of a finely granular substance (nwcleoplasma) starting out
from the germinative spot as a centre and embracing in its substance
the pseudo-nucleoli. The latter vary in size and in number (from 8
to 15), and may be spread through the whole vesicle, but usually are
situated in the vicinity of the true nucleolus, from which they differ in
being much less refractive.
, Of nuclei in general Van Beneden holds, that the young nucleus is
|formed of homogeneous matter, essence nucléaire. When it enlarges, the
jnuclear essence becomes united with a substance (suc nucléaire) taken
from the protoplasm of the young cell. The substance nucléaire which
results from this union constitutes the body of the nucleus. The mem-
brane of the definite nucleus and the nucleoli are unmodified remnants
of the primitive young nucleus ; they are formed exclusively of nuclear
‘essence. When a nucleus is about to divide, the nucleoli and the nuclear
‘membrane dissolve in the nuclear substance ; for this reason the contour
of the nucleus becomes very indistinct and the nucleoli disappear. After
i VOL, VI.— No. 12. 27
}
418 BULLETIN OF THE
this solution a complete separation ensues between the nuclear essence,
which goes to form the equatorial zone, and the nuclear fluid (swe),
which is repelled to the poles of the nucleus. After the division of the
zone into two nuclear disks which are to become the new nuclei, this
nuclear fluid loses itself in the body of the cell. The vacuoles of the
nucleoli are only the result of the momentary union of certain parts of
the nuclear swbstance with the nuclear fluid.
In the case of the nucleus of the central cell of Dicyema, the use of
osmic acid followed by picrocarminate results in giving the nuclear swb-
stance a rose color, the nucleolus and membrane a bright red, and in
leaving the reticular substance unstained.
In the disappearance of the germinative vesicle of Asteracanthion,
which takes place in exactly the same manner whether the eggs are
fertilized or not, the nucleoplasm and pseudo-nucleoli first disappear,
then the dot and the contour of the vesicle become paler, the vacuoles
of the dot become confluent, and the surface of the dot gradually be-
comes lobed and finally breaks up into a large number of fragments
which separate and spread through the whole vesicle. These fragments
increase a little in volume, become less refractive, and finally cease to
be visible. Some seconds after this the membrane of the vesicle be-
comes ruptured on the side toward the centre of the egg and parts of
its contents escape; the membrane finally dissolves away, and there
remains only a clear spot, with ill-defined and increasingly irregular con-
tour. The spot diminishes in size till it vanishes. Van Beneden saw
the polar globules * “ formed under his own eyes,” but is unable to give
any account of their real origin. All his observations appear to have
been made on living eggs, which accounts for his having overlooked
many facts.
The principal conclusions of VAN BaMBEKE ('76, pp. 99-117), reached
by the study of Pelobates, Triton, and Axolotl, have already (p. 389)
been stated. It only remains to add that he never observed the for-
mation of polar globules, but in eggs of the Axolotl, immersed in
alcohol immediately after fecundation, he discovered the existence of
a whitish spot at the niveau of, and all around, the fovea germinatiwa,
caused by a superficial layer of probably coagulated albuminoid matter,
which gradually thinned out toward its periphery. This layer presents
in section (Pl. Il. Figs. 5 and 6) a striation perpendicular to its sur
* By a double error of translation ‘‘corps directeurs (globules polaires)’” appears
in the English translation in the absurd form of ‘distinctive bodies and polar glob-
ules,”
MUSEUM OF COMPARATIVE ZOOLOGY. 419
face, and is strikingly similar to the veil-like layer seen by Oellacher
in the unimpregnated egg of the trout. Van Bambeke, however, objects
to Oellacher’s interpretation of this layer, as fur at least as regards
batrachians, since in the eggs of the latter the envelope of the germina-
tive vesicle never presents the characters pointed out by Oellacher for
the trout’s egg.
Greerr (76, pp. 34, 35) gives a short preliminary notice of early
stages of Asteracanthion rubens. The mature egg has two envelopes :
“Gallertzone ” and “Eihaut.” The yolk is composed of a homogeneous —
clear ‘‘Grundsubstanz” and two kinds of granules. The germinative
vesicle is clear, and has a distinct membrane; the germinative dot is
more compact, and embraces small round vesicles variable in number
and size. Delicate filaments, stretched through the space of the vesicle,
are beset with pearl-like nodules, and exhibit spontaneous motion and
branching. After fructification — or without it, if the egg remains a
time in pure sea-water — the vesicle disappears, but the germinative dot
persists. This, in the fecundated egg, mzgrates like an ameba through the
yolk. The latter assumes a radial appearance about the now centrally
located germinative dot. The polar globule appears with the first-seg-
mentation constriction, or even later. (!) Nothing of a spermatic nucleus
was seen, nor are the polar globules to be connected with spermatozoa.
GiaRD (76%, pp. 233, 234) traces early changes in the egg of one of
the sedentary annelids (Salmacina Dysteri) as follows. After fecunda-
tion the germinative vesicle ceases to be visible, and one observes the
appearance of a circular, finely granular spot at the surface of the egg,
over against which there are two polar globules. The spot in turn dis-
appears and the egg suffers a constriction /ess (?) pronounced on the side
where the spot was situated.
Besides the entire absence of the germinative vesicle in the excluded
eges of the spider (Philodromus), Lupwie (’'76, pp. 473, 479) contrib-
utes nothing which concerns us in this connection.
Strecker (’76°, p. 125) also reports for the eggs of Chthonius that the
germinative vesicle — after becoming more elongated, as seen in his
figures — entirely disappears, and near the place where it perishes a
_ brown round spot, composed of the “coarser granules ” of the proto-
”
plasm, makes its appearance. This undergoes division with the subse-
| guent total segmentation of the egg.
In a chapter first introduced into the second edition of his book on
“Zellbildung,” etc., StRasBuRGER (76, pp. 297-305, Taf. VII., VIII.)
discusses at some length the question of the fate of the germinative
a
420 BULLETIN OF THE
vesicle. Led by Hertwig’s studies on Toxopneustes to a re-examination
of this topic, he finds the opportunity, with improved methods of treat-
ing the eggs of Phallusia, to correct the statement in the first edition
to the effect that the mature eggs are altogether destitute of a nucleus,
By employing osmic acid on alcoholic preparations, he is able to demon-
strate the existence of a structure (Taf. VIII. Figs. 2, 3) which he
designates with Hertwig as Eikern. “Dieser Eikern,” says Strasburger,
‘liegt hier der Hautschicht nicht * an, ist derselben oft sogar angedriickt,
ausser dem aber von einer helleren Zone umgeben, die aber nicht scharf
gegen das angrenzende Protoplasma abgeschieden ist.” I question the
accuracy of the conclusion to which Strasburger here arrives. No one
has hitherto called attention, I believe, to the possibility of any other
interpretation for these figures than that which Strasburger himself
gives. Nothing can be further from my purpose than to cast doubt on
the persistence of nuclear substance in the egg. It is quite another
question if the flattened lens-shaped body represented in Strasburger’s
figures 2 and 3 (Taf. VIII.) is really this remaining nuclear substance.
The interpretation which I am inclined to give these figures is quite
different, and of some importance as bearing on the existence of polar
globules in the Tunicata. If, as I have no reason to doubt, Biitschli was
right in saying (’76, p. 384) that hitherto nothing had been observed ~
concerning polar globules among Tunicata, this will, in my opinion, be
the first evidence tending to show that such bodies are really produced
in that group of animals ; for I suspect that these figures represent a
stage just prior to the formation of a polar globule. This explanation
occurred to me when comparing Fig. 50 (Limax) with Strasburger’s fig-
ures. Much the most conspicuous part of Fig. 50 is the areal corpuscle
(aa') of the peripheral aster. Were the egg for any reason to become
less transparent, it is readily conceivable that all the other parts might
become indistinguishable and still leave this flattened oval structure
visible, and the surrounding radial system would then appear simply as
a less granular or clear zone, a condition of affairs, in other words, which
is completely realized in Strasburger’s figures. The features which make
it possible for me to maintain the identity of these two structures may
be stated as follows :—
(1.) The shape of Strasburger’s “ Eikern.” —I know of no case im
which the egg nucleus (female pronucleus) exhibits such a remarkable
form, — apparently that of a very much flattened biconvex lens of
which the thickness is (in Fig. 3) not over one fourth its diameter.
* This is evidently a typographical error for ‘‘dicht.”
MUSEUM OF COMPARATIVE ZOOLOGY. 4?1
When any considerable deviation from the spherical form of the female
pronucleus is noticeable, the latter will, I think, be found to be length-
ened rather than shortened along the polar axis of the egg. On the
other hand, this flattened condition is quite constant for the corpuscle
occupying the centre of the peripheral star of an archiamphiaster.*
(2.) The position of the “ EHikern” is such as to make quite improb-
able the interpretation given by Strasburger. It is true that, if a polar
globule is not formed here as in the majority of animals (viz. by the
division of a spindle body), then we have no right to assume the fulfil-
ment of all the conditions which obtain in such a process ; but granting
for the moment that here as elsewhere a polar globule is thus formed,
then the female pronucleus could hardly have the position close to the
surface, as given in the figure, much less the position indicated by the
words ‘“‘pressed against the Hautschicht.” The constriction which sepa-
rates the two unequal cells — polar globule and yolk sphere — divides
the spindle figure approximately in the middle. The interzonal fila-
ments must be reduced to zero in order to allow the lateral zone of
thickenings to form a new nucleus close to or in contact with the thin
cortical layer of the yolk. There is abundant evidence that the zone of
thickenings which pertains to the polar globule forms a nucleus in, or
beyond, the centre of the polar globule, therefore at some distance froin
its last formed surface;f and I recall numerous illustrations which
place the corresponding parts of the half-spindle remaining in the yolk
at an equal or greater distance from its surface,} — none which place
the female pronucleus so close to the surface as in the case of Phallusia,
if, perhaps, I make an exception of the case of Hippopodius figured by
Hertwig.§
If, on the other hand, one takes into account the migration of the
spindle as described for Limax, the fact that the corpuscle, aa’, occupies
a position close to the surface in the stage represented by Fig. 50, and
that it ultimately comes to be fused to the apex of the polar globule
(Fig. 63), then the interpretation I have given to Strasburger’s observa-
tions will find, I hope, sufficient justification. I will add a single pecu-
liarity further, which, though not prominent, may not be altogether
insignificant.
* Compare for Limax Figs. 43 and 48. See also Whitman’s (’78%, pp. 18-21,
Fig. 63. C. P.) account of it as “‘ the pellucid spot.”
t Compare for Limax, Fig. 40 ; also numerous figures by Biitschli, 0. Hertwig, and
others.
¥ See Biitschli’s figures in Strasburger, op. cit., Taf. VII. Figs. 13, 14.
§ O. Hertwig, "78%, p. 186, Taf. IX. Fig. 12 (wrongly numbered ‘‘ 9”).
12 BULLETIN OF THE
(3.) The surface of the egg in Strasburger’s Fig. 2 is slightly elevated
in the region of the questionable corpuscle, somewhat as in Figs. 43 and
50 of Limax.
I am well aware that serious objections to this view of the matter
may be raised. The entire absence of anything which could answer to
the spindle itself, the thickenings of its fibres, or the deeper sun, is at
first thought a weighty objection, and yet I can readily believe that in
eggs treated first with alcohol these structural peculiarities may have
been obscured by the opacity of the yolk, so that only those parts which
lay near the surface were distinguishable. Perhaps a more serious ob-
jection exists in the probability that the questionable corpuscles were
stained by treatment with osmic acid and Beale’s carmine. Strasburger,
I believe, does not say directly that such is the case; but even if it
was stained, I am not sure that on that account my explanation is to
be abandoned. Whitman ('78%, p. 18) says of the “ pellucid spot,”
the case of Clepsine, that it is deeply colored with carmine, and he too
made use of osmic acid. As far as regards this “ pellucid spot,” I think
I have reason to claim that it corresponds with the corpuscle in the
centre of the aster of Limax (aqa’), and is not derived from the nuclear
plate which Whitman, it is true, did not see, but which could hardly
have divided and migrated to the tips of the spindle at so early a
stage as is represented by his Fig. 63, or, still less, at the stage of his
Fig. 62. So far, then, I have indirect evidence that this flattened cor-
puscle may stain in osmic acid, and therefore am able to explain its
dark appearance in the figures given by Strasburger. I regret that
none of my preparations of this stage were made with osmic acid, as,
had they been, I might be able to add direct evidence of the staining
capacity of these areal corpuscles.
If this explanation be correct, we may confidently expect that the
polar globules and their mode of formation will be soon made clear to
us in tunicates, and thus one more group of animals be made to lend
evidence in support of a rational explanation of the phenomena of matu-
ration which shall be applicable to all the higher animals, if not to all
organisms. *
* P, S.— By the last paper of O. Hertwig (’78%, p. 191) my attention has been
called to a preliminary notice by Fol (’77*, p. 339), in which he mentions the exist-
ence of two polar globules in the case of Phallusia, that I had entirely overlooked.
The oversight was due to the incomplete manner in which the contents were indi-
cated on the cover of the magazine in which Fol’s article is published. He has two
articles in the October number of the magazine, but his name appears only once on
te,
eoeteen
ee
aie
ste cere es
ME NOE ee A
MUSEUM OF COMPARATIVE ZOOLOGY. 48
In his criticism of Hertwig, Strasburger endeavors to show the impos-
sibility of accepting the view that the germinative dot persists. Besides
the numerous results of other observers which seem irreconcilable with
it, a prime objection is, that it leaves no chance for the existence of polar
globules, which Biitschli and Fol have connected in their origin with
the germinative vesicle. One has only to assume that the half, and not
the whole, of Biitschli’s spindle is ejected, the other half remaining in the
egg, in order to bring his own (Strasburger’s) observations on the “ canal
cells” of conifers into harmony with the results of Biitschli and Fol.
For Strasburger (doc. czt., pp. 293-297 and 18-21) makes the very
important discovery that in conifers the so-called canal cells present in
their formation points of resemblance to the polar globules of animal eggs.
After the cell nucleus has remained some time at the end of the ege
which is to receive the pollen tube, it is divided a short time before th>
fecundation into halves which are at once separated by a ‘“ Hautschicht-
platte.” One half, which is accompanied by only a very small amount
of protoplasm, becomes the nucleus of the canal cell ; the other half
remains in the egg and in migrating from the pole leaves stretched
behind it fibres [interzonal filaments], which in turn disappear while
the nucleus, increasing in size, advances to the centre of the egg. This
is the “ EKikern” (female pronucleus). The formerly expressed idea
that the canal cell is a rudimentary structure without recognizable
function is to be modified, inasmuch as it is the equivalent of the polar
globules, and by its formation the nucleus of the primitive egg (Eian-
lage) frees itself of certain ingredients, and thus prepares for the ap-
proaching fructification. The protoplasm of the canal cell perishes
without function. He also finds the canal cell in Cycas. For mosses
and vascular cryptogams, however, only the “‘ Bauchkanalzelle” is to be
the cover. Having found the first article, the existence of a second, which occurs
some pages farther on, was not suspected.
Fol’s description is limited to saying that the polar globules arise after the disap-
pearance of the germinative vesicle, and are produced by a process of cell division.
As this notice is not accompanied by figures, one is left without the means of
definitely confirming or rejecting the opinion I have expressed above about the
eggs studied by Strasburger ; the mere announcement, however, that polar globules
have been seen, only gives greater probability to my explanation.
Since writing the above, I have been able to consult Stossich (77, p. 225), and
find that he states, in a criticism of Rabl’s theory of the significance of the polar
globules, that he has found these directive vesicles ‘‘in eggs of serpulas, ascidians,
and other animals subject to regular segmentation.” This paper antedates that of
Fol by some three months, but does not contain any description especially devoted
to the formation of polar globules in the ascidians.
424 BULLETIN OF THE
considered as the equivalent of the canal cell of conifers. The so-called
‘“‘Fadenapparat ” of the egg of angiosperms has also rightly been held
in Strasburger’s opinion to be homologous with the canal cells.
Strasburger concludes (pp. 304, 305) that a part of the germinative —
vesicle in the animal egg always remains behind, but that this relic does
not correspond to the germinative dot. Thus it is more than probable
that there is an agreement with corresponding processes in plants,
where one half of the divided egg nucleus is eliminated, and the other
half is modified in one way or another, and may even become indistin-
guishable. :
PRIESTLEY (’76) gives a purely objective résumé of the papers of Auer-
bach (’74), Strasburger (’75), O. Hertwig (’75), and Van Beneden (’75).
GREEFF (’76%, pp. 85-87) takes a position intermediate between Van
Beneden and O. Hertwig. He in the main corroborates for Asteracan-
thion Van Beneden’s observations, by saying, that the germinative dot
first suffers a conversion into granules, that the vesicle then begins to
diminish in size and distinctness, and that finally both appear to
vanish ; and then he concludes by saying, ‘‘ One cannot positively deny
that the germinative spot persists, and, in migrating through the yolk,
ameceba-like, becomes so indistinct as to be no longer distinguishable.”
He also reports that eggs of A. rubens carefully guarded from fecunda- —
tion develop in the normal manner, but considerably slower than fecun-
dated eggs (pp. 83-85).
SELENKA ("76% p. 167) writes of the freshly deposited eggs of Cucuma-
ria, that they no longer possess a nucleus, but exhibit at times “a little
drop of protoplasm under the egg capsule,— perhaps the excrement of
the egg.” This is probably to be considered the polar globule. “In
the course of one or a few hours a clear nuclear area (Kernhof) becomes
visible in the interior, in the middle of which arise new nuclei, composed
of eight to twenty small bodies (Kernkeime, Goette) united in the form
of a mulberry.” Up to a stage consisting of thirty-two segmentation
spheres the same peculiar groups of Kernkeime are met with. After-
wards the nuclei take the form of smooth balls, destitute of enveloping
clear areas.
Satensky (76, p. 185, Taf. XIV. Fig. 5) figures an egg of Salpa
in which two nuclei [the pronuclei] occupy the opposite poles. I
believe Salensky is wrong in holding the presence of these nuclei to be
evidence of approaching segmentation.
ZELLER ('76, pp. 255 — 260, Taf. XVIII. Figs. 21 — 31) gives an interest-
ing account of the processes accompanying cell division, and also some
MUSEUM OF COMPARATIVE ZOOLOGY. 425
observations on the maturation of the ovum of Polystomum integerri-
.mum. A thickening of the yolk forces the germinative vesicle to one
side of the egg, when its section becomes more or less crescentic. The
yesicle disappears, leaving behind only a homogeneous light space and
faint indications of radiation. The spherical form of the yolk is ex-
changed for a more flattened one. Two nuclear structures appear near
the surface after the egg has resumed its spherical condition, and unite in
the middle of the yolk to form a nucleus which soon disappears.
Another case of misinterpretation of the pronuclei similar to Salen-
sky’s is that of Barrots (’76, p. 16, Pl. XII. Fig. 2), who says, “ Certain
eggs {before segmentation] present two nuclei; they are the nuclei of
the first two spheres of segmentation.”
Ep. van BenepEN ('76", p. 49) thinks the germs of the infusoriform
embryos of Dicyema do not lose their nuclei, as eggs do their germina-
tive vesicles, but that the nucleus divides, and thus gives rise to the
nuclei of the first two embryonic cells.
Bosretzky’s ('76, pp. 97, 98, 100) observations on the stages em-
braced under maturation are very limited. At a point on the surface
of the freshly laid egg of Nassa mutabilis a small whitish spot is to be
seen. Nothing is said about the way the polar globules are formed ;
but there are two recognizable with each egg soon after the extrusion of
the latter, and they are joined to the egg near the centre of the white
spot, by a delicate filament. A nucleus is no longer to be found; once,
however, when the polar globules were both formed, the nucleus [female
pronucleus ?] could. be distinctly seen immediately under the surface of
the ege, but there was no nucleolus; the nucleus was homogeneous, and
looked like a vacuole. There is a nucleus-like corpuscle inside the polar
globules, which gives to them the appearance of small cells.
RaBu gives an account (76, pp. 316, 317, Taf. X. Figs. 4-60),
and apparently very accurate figures, of the formation of the second
polar globule in Unio, so far, at least, as can be seen on living eggs.
_ More than two polar globules were never observed, nor was the second
ever produced by a division of the first. The first is usually somewhat
larger than the second. He also figures at the vegetative pole a cone-
like elevation, which has not entirely disappeared when the second
globule is forming. ‘The egg is without a germinative yesicle.
In a lengthy consideration of the significance of the polar globules
(pp. 331-338) Rabl combats the notion that their elimination is
comparable to an act of defecation; for one would then be compelled,
he says, to assume quite different physiological processes for the first
426 BULLETIN OF THE
stages of development in cases when no polar globules are formed. He
then urges in support of his “ protective” theory, — (1.) that, as a rule,
_ the polar globules accompany only the “ inequal” method of segmenta-
tion; (2.) that the place of their origin is always the animal pole of
the germ ; and (3.) that the specific gravity of the animal pole is less
than that of the opposite pole in cases of inequal segmentation. From
all this Rabl concludes that the polar globules serve the purpose of
elastic balls in preventing the dangerous pressure of the germ against
the membrane of the egg. For the ascidians with their primordial
segmentation, the pressure being uniform on all sides, not a few, but a
large number, of these elastic balls (Testazellen) are provided.
However ingenious this theory may at first sight appear, it cannot
claim to be based upon satisfactory grounds, and I am the more sur-
prised that Rabl should have promulgated it in connection with his
previous paper on pulmonate mollusks, since in that case such a rela-
tively enormous distance intervenes between the “ Eiweisshiille” and
the embryo, —a distance so great that one rarely finds the yolk even
in the vicinity of the membrane of the albumen until rotation begins,
and then, as the author himself admits, this protective function must
cease to exist. Apart from the absence of proof that such protection is
needed, or is even advantageous to the embryo, or that the polar
globules are capable of offering such protection, the links in his chain
of argumentation seem to be exceedingly fragile. All authentic obser-
vations, it is true, go to show that there exists the constant relation
between polar globule and the promorphology of the egg which Rabl
has expressed by saying the globule is formed at the animal pole of the
germ. That, however, is only the connecting link between two others.
I believe the evidence is still wanting to prove that the animal pole of
the egg is specifically the lighter in all cases of inequal segmentation, or,
at least, that the difference in specific gravity is sufficient to cause the
germ to rest with the animal pole uppermost. My own observations
in the case of Limax have not afforded the least ground for such a
conclusion. The yolks of eggs left undisturbed for hours have been
found to present the same want of uniformity in position,which is met
with under any other circumstances ; individual eggs have been ob-
served for a long time during the early stages of segmentation, the polar
globules remaining all the time in such a position as to be seen outside
the profile of the yolk. Furthermore, it seems to me, this theory
necessitates the assumption that the yolk (or embryo) is specifically
lighter than the enveloping medium, otherwise there would be no
MUSEUM OF COMPARATIVE ZOOLOGY. AT
pressure of the embryo against the membrane directly above it ; but
we have not yet the proof that such is universally the case when polar
globules exist. The difference in specific gravity will presumably be too
little, in most cases, to cause any appreciable pressure in ether direction
along the vertical axis. It is, however, quite another question whether
polar globules are ccenogenetic phenomena. Rabl certainly deserves
credit for having turned the discussion concerning polar globules in a
phylogenetic direction, and, unsatisfactory as his protection theory
seems, it does not necessarily follow that there is no ground for his
claim that the polar globules are comparatively recent acquisitions. If
the globules were limited, as he claims, to eggs with unequal segmenta-
tion, there would certainly exist good reason to infer that they were
in some way adaptive acquisitions of this latter class of eggs. But the
following are a few of the many exceptions which make it improbable
that polar globules are ccenogenetic adaptations to unequal cleavage ;
Hydra (Kleinenberg, "72, pp. 46, 47, 51); Lucernaria (Korotneff, 76,
p. 393); Hippopodius, Sagitta, and Echinoderms (O. Hertwig, "787).
Indeed, if Strasburger is right in maintaining that the canal cells of
conifers, and equivalent cells of both lower and higher plants, are ho-
mologous with polar globules, we must apparently go back to a very
early point in the history of organisms to discover the origin and true
significance of these cells, unless it is assumed they have been separately
acquired by the two recognized groups of higher organisms.
Rabl has realized the sentiment of Von Baer’s with which he closes
| his last paper: “Irrige, aber bestimmt ausgesprochene allgemeine Re-
| sultate haben durch die Berichtigung, die sie veranlassen, und die
| scharfere Beachtung aller Verhiltnisse, zu der sie nothigen, der Wissen-
| schaft fast immer mehr geniitzt, als vorsichtiges Zuriickhalten in dieser
Sphare.”
StossicH (76) entertains views of the morphology of the egg which
} are at variance with well-established information. He is apparently
| influenced in his opinion by the study of the germinative vesicle under-
| going metamorphosis. |
| The egg, he says, is a cell, but the nucleus of this cell is not the’
i germinative vesicle; it is the germinative dot, and within it may be
i found the nucleolus. The body of the cell, i. e. the yolk, is composed
| of two layers, — an external, adapted to the formation of granules, and
an internal (germinative vesicle), homogeneous and hyaline, in which
are contained the nucleus and nucleolus. The so-called germinative
} e . . . . . . .
vesicle is not, in his opinion, a vesicle having a proper membrane,
|
|
428 BULLETIN OF THE
but really an optical effect produced by the differentiation of the
protoplasm.
If it is not the nucleus of the first segmentation sphere which hag
misled the author into denying the existence of a membrane, it must be
that he has only seen the germinative vesicle after the beginning of its
metamorphosis. If there were previously any chance for doubt, the
peculiar spindle shape which both nucleus and germinative vesicle
assume now proves sufficiently the morphological equivalency of the
two structures.
Immediately upon contact with the fecundating element in the case
of Serpula the granules of the yolk are much increased, and are seen
undergoing a slow rotary motion; this causes an opacity of the yolk
which renders the internal layer (germinative vesicle) almost invisible.
The latter, therefore, does not disappear, but is simply obscured. This
formation of granulations is not simply a mechanical alteration, but is
accompanied by a chemical process that eliminates from the yolk
certain secondary liquid and gaseous products which accumulate be-
tween the yolk and its membrane; it is thus that the yolk becomes
somewhat contracted and the membrane much dilated. In consequence
of the formation of granulations the external layer of the yolk becomes
more dense, and therefore the internal layer (germinative vesicle), being
less dense, is obliged to ascend to the surface of the yolk, and thus one
pole of the egg becomes clearer than the opposite pole. When the
vesicle has reached the superior pole of the egg, the vitelline membrane
is resorbed and an aperture formed through which the vesicle escapes
in the form of two or three drops, — “directive vesicles,” — which
remain between the membrane and the yolk. These directive vesicles
only serve to determine the point of departure and the direction of the
first cleavage furrow.*
The latter is not, however, the first indication of segmentation.
After the formation of the directive vesicles the rotary motion of the
granules ceases, and they are gradually arranged in two groups between
which the plane of division is to pass. The granulations do not remain
quite fixed, but are disposed in rays which depart from the centre of
each group. Gradually this centre enlarges until it acquires the form
of a nucleus, so that the rays produced from the granulations no longer
depart from a point, but from a circle. As the furrow of segmentation
advances, the rays become more uncertain.
* It is an error for Stossich to connect with this view the name of “the distin-
guished Miiller, father of embryology,” instead of that of Friedrich Miiller.
MUSEUM OF COMPARATIVE ZOOLOGY. 499
Stossich seems to have made, with some other observers, the mistake
of confounding the astral areas with new nuclei.
Fou (76, pp. 111-113, 188-145, Pl. IV. Fig. 3) describes, but does
not very fully illustrate, the phenomena of maturation in the Hetero-
pods. “The nucleus had already disappeared in all the eggs (Firo-
loides) which I have observed, to reappear before and after the escape
of the corpuscules, de rebut.” This statement, with some parts of the
immediately following description, is certainly unique. Perhaps the
account may be the result of a faulty combination of observations.
Fol gives for Pterotrachea the details of the changes, of which the
above quotation is an epitome, as follows. The molecular star has the
same appearance as in Pteropods. There is, however, this difference,
that the protoplasm is so scanty as to form only a thin layer between
the nucleus * and the “ protolécithe.” When the nucleus [germinative
vesicle ?] has vanished, the vitellus appears composed merely of two very
clearly marked spheres set concentrically one within the other. The
sphere within is nothing else than the protoplasm, the greatest part,
but not the whole, of which surrounds itself with a membrane, and be-
comes a central nucleus. At opposite (nutritive and formative) poles of
this nucleus there soon appear two centres of attraction whence proto-
plasmic rays emerge in all directions [first archiamphiaster]. The
stouter of these striations stretch from one centre to the other in the
interior of the nucleus. The limits of the latter disappear and the
stars move apart. . Biitschli’s fusiform body is only the central part of
the vanished nucleus. As to the fibres of the spindle, they are only
Striations in the protoplasm. One of the stars approaches the centre,
the other nears one pole of the vitellus and there gives rise to the first
polar globule. In the interior of the globule is readily to be distin-
guished the termination of the spindle fibres (Biitschli), which have
their centre at the middle of the exterior extremity of the globule.
There enlargements of these strie are also to be observed. The star
in the vitellus now divides anew, without having taken the form of a
: nucleus. During this division the striations, arranged in the spindle
| form, reappear. Then the second globule is formed, in the same man-
}
* It is often difficult to comprehend Fol’s meaning because he uses the term
“nucleus” in the most general sense, when accuracy demands a more explicit term.
Here, for example, he speaks of the existence of a nucleus where, to judge from what
has preceded (Firoloides and Pteropoda), one has. the right to suppose that the
| germinative vesicle has been supplanted by a molecular star, and that consequently
| there is no nucleus.
|
|
430 BULLETIN OF THE
ner as the first. After the escape of the [second] polar globule, that
which remains of the star approaches again the centre of the vitellus,
and becomes rounded in the form of a nucleus. The nucleus not only
disappears before each segmentation, but it twzce becomes fused with —
the surrounding protoplasm and twice individualized before the first
segmentation.
In this description that which least coincides with the ideas I have
formed from my own observations and those of others is the statement
made in the last sentence, together with that which makes the nucleus
(germinative vesicle) disappear, and again appear before the formation
of the polar globule. Although recognizing the spindle fibres as stouter
than the remaining rays, Fol does not admit any fundamental difference
between the two. The equatorial thickenings were not seen, and the
lateral zones only in the formed polar globule. I have elsewhere stated
my reasons for inferring that the changes succeeding the formation of
the first polar globule are more complicated than has hitherto been
assumed by Fol or any other observer.
I wish to call attention to only one or two points in his critical
review of other authors and in his “reflexions.” Touching the réle of
the nucleus, Fol says: ‘It cannot serve as a centre of attraction pre-
siding over cellular division, since these centres of attraction arise at
the very limit of nucleus and protoplasm, and since the nucleus, if so
be that it is able to persist and divide, would undergo these successive
modifications only in.a manner altogether passive, at least as passive
as the cell or the segmentation sphere in which it is situated.” And
again, ‘‘ Il ne se divise pas, il est divisé.” I believe there are very good
grounds for adopting this opinion.
The fibres of Biitschli are filaments of sarcode, according to Fol, and
the grains (thickenings) are varicosities of the filaments, which have
nothing whatever to do with the nucleoli. This is the first paper, I be-
lieve, in which Fol admits that the nucleus does not appear to be dis-
solved. It changes in volume and appearance, and loses its contour,
he says, and its substance obeys the call of the centres of attraction,
which, so to speak, tear it in two.
Biscuit (76, pp. 215 — 249, 380 — 394, Taf. I. - IV.) contributes val-
uable information on the features of maturation in eggs of worms and
gasteropods, a part of which was made known in his preliminary account.
In Nephelis the youngest eggs studied exhibit near the somewhat flat-
tened pole the spindle-shaped body already described, lying with its axis
nearly in the axis of the egg. A broad equatorial zone of thickenings
MUSEUM OF COMPARATIVE ZOOLOGY. 431
occupies the middle of the spindle. Around each of its ends is a clear
homogeneous area, and outside this the yolk granules are arranged in
radial lines, thus forming two suns. The “area” passes gradually into
the surrounding granular yolk. The spindle is the metamorphosed ger-
minative vesicle. It is ejected * from the yolk, not in the simple torm
previously described for Cucullanus, but in several vesicular portions
which apparently enlarge by swelling up, and are united to each other
by narrow necks. The constrictions are due to an active process of
nuclear division. Of the three portions of this ejected nucleus (now
a polar globule) the first is the smallest, the last the largest. During
the early stages of this elimination the part within the yolk retains its
spindle form, and a zone of dark granules is found at [near] this end of
the spindle, as well as in the part of the polar globule already eliminated.
The latter zone is joined by delicate filaments with the filaments within
the yolk. Ultimately the whole of the spindle is eliminated. The first
and second portions of the polar globules subsequently unite, and a clear
vesicle [nucleus] often makes its appearance therein.
The female pronucleus was observed at an early stage, but no connec-
tion with the spindle was detected. The changes in Cucullanus have
already (p. 404) been given. I will add, that Biitschli (doc. cit., p. 224)
judges, from the appearance of the optical cross-section of the spindle,
that the nuclear plate lies within a definitely circumscribed body, there-
fore cannot be a simple differentiation in the yolk. The protoplasm
immediately underlying the ejected spindle is for a certain distance
clearer and more coarsely granular than the rest of the yolk, from
which it is quite sharply defined. This clear protoplasm probably
spreads over the surface of the vitellus and is the seat of the formation
_ of the new nuclei, since the latter arise close under the surface at widely
separated places.
* T am not quite satisfied what share Biitschli intends to ascribe to the astral
rays in this process of elimination. He says (p. 216): ‘‘ Etwas spatere Stadien zei-
gen nun, dass die um das einé Ende des spindelformigen Korpers befindliche Dot-
terstrahlung bis in die Oberflache des Dotters geriickt ist und der spindelférmig
metamorphosirte Kern sich durch diese Strahlung aus der Oberfliiche des Dotters
' hervorzuschieben beginnt.” I think he has nowhere else intimated that the rays
were an agent in the propulsion of a nuclear mass, and it is therefore barely possible
| that here he only means to say that the nucleus makes its way through (hindurch)
| the peripheral aster. But the more literal reading makes the rays the agent of the
| ejection. It is in this sense that O. Hertwig (’77, p. 5) understands the author when
| he paraphrases his description by saying : ‘‘Die Kernspindel . . . . wird von einer hier
)
|
)
432 BULLETIN OF THE
The least intelligible part of the observations on Cucullanus is the total
ejection of the spindle in an undiwded state, and its resting intact on the
surface of the yolk. This is less likely to be a normal condition of affairs
from the fact that stages in the formation of the polar globule quite like
those observed in other animals were seen and figured by Biitschli.
Observations on several non-parasitic nematodes contribute nothing of
special interest concerning the formation of the polar globules, but con-
firm the existence of two pronuclei which ultimately become fused.
The observations on Lymneus and Succinea confirm the conclusions
reached with Nephelis. The earliest eggs studied exhibit a flattened
yolk ; one of the poles of the axis thus determined is characterized by a
low, broad, conical elevation of clear protoplasm. In the short axis lie
two “areas” and their suns, one near the centre, the other nearer the
elevated pole, and between the two stretch curved fibres (spindle body).
Zones of thickenings do not seem to have been observed till the polar
globule was already formed, at least none are figured. This spindle figure
migrates toward the surface till one of the ‘“‘ areas” comes to lie in the —
surface of the elevated portion of the yolk. This area does not seem to
have exhibited any central flattened corpuscle such as Limax shows ; but
aside from this and the absence of lateral zones the stage represented in
Fig. 2, Taf. IV. of Biitschli’s work corresponds very closely with Fig. 50
of Limax. The polar globule is produced as in Nephelis, but the author
thinks he has seen the already formed second globule lying still within
the yolk, and joined to the globule already ejected by a slender pedicel,
an observation that one cannot now expect to see confirmed. There
is some confusion in his mind regarding the persistence of these two sys-
tems of rays, apparently resulting from an incomplete conception of the
relation of the polar globules to the spindle. The protoplasm found at
this pole immediately after the ejection of the first polar globule is lim-
ited by a sharp but feebly expressed boundary from the granular proto-
plasm of the yolk. I have never seen it so sharply defined as he portrays
it in his Figs. 3, 5, and 17, Taf. 1V. It was this feature which helped
to mislead the author into the earlier belief that a remnant of the ger-
minative vesicle remained behind in a recognizable form.
As to the formation of a new nucleus Biitschli says that close under
the surface where the polar globules are formed there appear in Lymneous
a number (nine or more) of small nuclei close together. Each possesses
a distinct dark membrane, and, within the clear fluid contents, a few dark
corpuscles with clear centres. The latter adhere closely to the mem-
brane. These nuclei melt together, so that at a later stage, although
MUSEUM OF COMPARATIVE ZOOLOGY. 433
retaining the same structure, they are fewer and larger. As they in-
crease in size, the corpuscles increase in number. At length there are
only two large nuclei, and these finally become united. In Succinea
there are never more than two, and they may arise far apart.
Studies on Rotifera and the pseudova of Aphidz only resulted in show-
ing that no elimination took place, although the germinative vesicle un-
derwent regressive changes and became indistinguishable.
On the streneth of his own observations upon the fate of the germina-
tive vesicle, Biitschli comes to the conclusion that it is possible to explain
divergences of opinion, and, in particular, that the steps supposed to be
preparatory to division are referable to the formation of a spindle and
stellar figures, but that this apparent preparation for division never leads
_ to that definite end, inasmuch as a process of expulsion supervenes. His
belief that only the vesicle was expelled, and that the whole of the spin-
dle body suffered this fate, compelled Biitschli to assume that, on the one
hand, the extruded mass in certain cases (Nephelis) increased in volume
by a process of swelling, and that, on the other hand, the germinative
vesicle might suffer a reduction in size by the loss of fluid constituents
during its conversion into a spindle. Thus were the differences in volume
between vesicle, spindle body, and polar globules to be explained. It is
now certainly established by his observations, he thinks, that the Rich-
tungsblaschen in snails, nematodes, and leeches represent the ejected ger-
minative vesicle, and most likely the whole of it, since none of his obser-
vations indicate that any remnant of the vesicle is left behind save the fluid
elements which escape at the time of its metamorphosis into a spindle.
Biitschli thinks that the structure held by Oellacher to be the radially
striate membrane of the germinative vesicle in the trout should not be
interpreted in that way; on the contrary, it is a modified portion of the
yolk, and is to be considered as the equivalent of the radial striations
which have been observed by himself and Fol. Such being the case, the
real extrusion of the germinative vesicle occurs later than Oellacher
maintains, viz. only after fecundation. Numerous other special cases,
which appear to controvert his ideas of the connection of fertilization
with the extrusion of the vesicle, he thinks can be explained by the fact
| that the vesicle seems to disappear, but really assumes the spindle condi-
| tion, and is not actually eliminated before fecundation.
In an appendix devoted to a refutation of O. Hertwig’s idea that the
germinative dot persists as the “ Hikern,” Biitschli (pp. 432-437) ex-
| presses the opinion that this “egg nucleus” may in the case of Toxo-
| pneustes represent the whole germinative vesicle, reduced in size after
}
} VOL. VI.— NO. 12. 28
ii
{
|
’
t
434 BULLETIN OF THE
the disappearance of the dot, or at least a part of it ; but in general one
must conclude from his own observations, as well as those of other ob-
servers (Strasburger, Flemming), that the nucleus, metamorphosed into —
a spindle, is ejected from the yolk. From his own studies he finds no
occasion for assuming that this ejection is incomplete. Still, in view of
the positive evidence that in conifers a portion of the egg nucleus, as
shown by Strasburger, remains behind, he is compelled to admit that
he cannot with absolute certainty deny that a part of the nuclear plate
of the metamorphosed egg nucleus becomes detached during the elimi-
nation to form the basis of one or several of the little nuclei which after-
wards appear in the yolk. Two points in his own observations may
also be favorable to this view: the origin of the new nuclei in definite
spatial relation to the place where the nucleus is ejected, and the ap-
parent connection (in Nephelis) of the eliminated egg nucleus with some —
of the newly formed nuclei by means of fine filaments.
The signification of the polar globules as understood by Biitschli will
be further considered in connection with the subject of fecundation. _
Korotnerr ('76, pp. 392-394, Pl. XVI. Figs. 10-13) reports for
Lucernaria the existence of a micropyle, which is quite readily seen in
fresh eggs. He says it is placed in a depression. It appears as a round
clear spot (Fig. 12) when seen from above. The germinative vesicle at
the maturity of the egg moves from the interior to the surface. At the
same time it takes on an elliptical form and zs peripheral extremity ap-
pears to become fused with the vitelline membrane. “ It has appeared to
me,” adds Korotneff, “ that the micropyle is always formed at the place of
this union.”
From the latter part of this description, which I have taken the lib-
erty to italicize, I think it is nearly certain that the supposed micropyle
is the same as the “ pellucid spot” seen by Whitman, — the corpuscle
in the central area of the superficial star of the archiamphiaster. It is
peculiar, and perhaps an objection to this view, that the surface of the
ego is at this point depressed rather than elevated, yet a like peculiar-
ity is to be observed in eggs of Pterotrachea. (O. Hertwig, "78%, p. 208,
Taf. XI. Fig. 8.) However that may prove to be, I think this explana-
tion will not be found to contravene any of the further observations
made by Korotneff, who finds in freshly deposited eggs that a globule *
* Korotneff erroneously holds this polar globule to be the expelled germinative
dot, just as Lovén and others have long ago done.
It is only a typographical error, which here (p. 393) makes Lovell responsible for
the idea that the nucleus (instead of nucleolus) escapes as polar globule.
MUSEUM OF COMPARATIVE ZOOLOGY. 435
occupies this depression in the surface of the yolk, when only a trace of
the germinative vesicle is to be seen (Joc. cit., Fig. 13). The failure to
make use of proper reagents is sufficient to explain the absence of every
thing relating to the internal appearance of the egg at this time.
ScHENK ('77) claims for the germinative dot of Serpula nearly the
same function which was ascribed by F. Miller to the ‘ Richtungsbliis-
chen.” On a former occasion he did not find polar globules, but instead
a flattened body which became pressed into the yolk and ceased to be
visible. He now maintains that this structure can be considered the
expelled germinative dot, for after fecundation one can follow it from its
existence within the germinative vesicle until its complete emergence
from the egg. After its exit, it is at first round, and only later becomes
flat ; or on the same egg there may be an alternation of these forms.
The appearance of this corpuscle is followed by the well-known retrac-
tion of the vitellus and the appearance of a radial striation in the pro-
toplasm of the egg. This eliminated dot exercises in part the function
of polar globule ; it exerts a mechanical or other influence over the
yolk which leads to the production of furrows,—an impulse to cleav-
age. It is difficult to say whether the dot communicates this impulse
through some ‘Impression in den Dotter,” or whether some other
stimulus is present.
The grounds urged for this opinion do not appear to me of great
moment. The elimination of the corpuscle at the point of the surface
where the first furrow is soon to appear, and the existence of the cor-
puscle in the furrow when the latter does appear, are sufficient to show
that accurate observations will make of this corpuscle a polar globule,
but not sufficient to give support to the theory here propounded.
In a note on fecundation Fou (’77) takes the position that there are
two well-marked cases in early stages of development: in one, which is
exemplified by the sea-urchin, there is a complete absence of the “ cor-
puscule de rebut,” the ovule at the moment of extrusion being already
destitute of germinative vesicle and possessing only a female pronucleus ;
in the other case, embracing most other animals, the vesicle is replaced
by a double stellate figure, one of the stars escapes to form the first
polar globule, and the second polar globule may be formed by a division
of the first, or, more often, like the first, by the formation of a second
double star. The substance thus expelled corresponds to the major
part of the germinative vesicle enveloped by a little vitelline protoplasm.
The principal difference in these two cases consists in the epoch of the
disappearance of the germinative vesicle, whether precocious or tardy.
436 BULLETIN OF THE
In a subsequent note Fou ('77") gives the results of recent studies on
Asterias glacialis. When the ovule comes into the sea-water the germi- —
native vesicle shrivels and in some way melts in the vitellus; its contents
do not escape, as Van Beneden thought. The germinative spot also loses
its sharp contour, becomes pale, often changes form, continues to dimin-
ish, and finally dissolves. Then there remain in the yolk only two ill
defined spots, one where the vesicle was located, the other, of ovoid form,
approaches the surface. The use of reagents discloses the existence of
a double star, which Fol names amphiaster. In its neutral plane this
amphiaster often presents bodies of an irregular form which he con-
siders as the remnant of the membrane of the germinative vesicle. This
is, I believe, the first time Fol records his observation of anything
answering to an equatorial nuclear disk.* The remnant of the dot is
still visible at some distance from this “ amphiaster de rebut,” but the
author “dares not affirm that no fragment of the germinative dot can
enter into the composition of this amphiaster.” He afterwards, how-
ever, asserts that the female pronucleus has no genetic connection with the
nucleolus of the ovule. Fol thinks this first stellate figure (amphzaster) is
not yet that which gives rise to the ‘“corpuscules de rebut,” but that it
divides within the yolk in such a manner that its peripheral star alone
gives rise to the amphiaster which is to be expelled. Thus, it is evident
according to his description, that there must at one time be at least three
stellate figures in the yolk. May he not have mistaken the star of a
male pronucleus for one of these three? At least I see no other explana-
tion of this statement, for it is quite improbable that any such division
as he indicates really takes place in the first amphiaster.
The internal half of the ‘‘ amphiaster de rebut” doubles, and the sec-
ond globule is formed like the first ; the internal half of this amphiaster
changes into a small spot, and becomes a female pronucleus, which
migrates toward, but does not reach, the centre of the yolk. These
changes are all effected in the same manner, whether fecundation
has preceded or not; if fecundation does not now follow, the egg
gradually decomposes. It was never seen to develop parthenogenet-
ically.
O. Hertwic (77) arrives at important conclusions from studies com-
municated in his second paper on “ Bildung, Befruchtung und Theilung
des thierischen Eies.” The observations were made on eggs of Hiru-
dinea and Rana. To the investigation of the former Hertwig was led
by the researches of Biitschli, and undertook their study with the pur-
* Consult in this connection pp. 429, 430.
MUSEUM OF COMPARATIVE ZOOLOGY. 437
pose of answering three questions which were left by Biitschli in an
unsatisfactory condition: (1.) how the germinative vesicle transforms
itself into the nuclear spindle ; (2.) whether the fecundation is of in-
fluence on the origin of the nuclear spindle and the polar globules; and
(3.) whether the nucleus (germinative vesicle) is completely eliminated,
or is partly retained and passes into the segmentation nuclei.
The ovarian eggs of Hemopis contain a comparatively small germi-
native vesicle with membrane in which are found a single nucleolus and
accessory nucleoli; the latter are stained deeply in osmic acid and
carmine. For this reason they are both to be considered nuclear sub-
stance. At maturity the nucleolus divides, and the nuclear membrane
dissolves so that there remains in the egg only a clear spot destitute of
granules in which parts of the stained nucleolus are observable. One
finds in place of this a spindle, which is variously situated, either near
the centre of the yolk, or more to one side, and then often with its axis
radially placed, one end being at the surface. When centrally located
it is surrounded by the same clear area which surrounds the fragments
of the nucleolus at an earlier stage. The fibres of the spindle converge
in two points, which are sharply expressed in Hertwig’s drawings; they
are formed, he says, of compacted nuclear substance, which takes the form
of a single dark nucleus (Kern) or several such. This is surrounded by
a clear area of protoplasm, around which the yolk granules have a radial
arrangement. The middle gone of thickenings becomes especially prom-
inent when the egg is treated with reagents. Hertwig considers as
stages in the process of the formation of the spindle, (1.) a condition in
which there are in the middle of the egg two homogeneous areas close
together, around which the yolk granules are arranged in rays, — there
being between these two systems a number of dark, coagulated, irrezu-
larly formed corpuscles, which have the appearance of nuclear substance;
and (2.) a condition in which there is found in place of these corpuscles
an indistinctly limited structure of approximately spindle shape, in the
middle of which are found small condensed granules not yet arranged
into a regular granular disk.
From these observations he finds reason to dissent from Biitschli’s
view that the spindle is the entire germinative vesicle metamorphosed.
He disagrees because of the great difference in the size of these two forms
of the nucleus ; the absence of a distinct membrane about the spindle ;
and the condition of the egg, so often met with, in which the germina-
tive dot or its fragments were the only parts of the vesicle that were
preserved. Hertwig does not deny a genetic connection between the
438 BULLETIN OF THE
two forms of nucleus ; on the contrary, this connection is supported by
the following facts : —
1. They both occupy the same position in the yolk.
2. The clear non-granular area which surrounds the centrally located
spindle corresponds very nearly with the size of the germinative vesicle
and appears to result from its dissolution.
3. An enuclear condition of the egg, if properly treated, could never
be made out.
4. The evidences of the dissolution of the germinative vesicle and the
formation of a spindle can be arranged in a continuous series.
“At maturity of the egg,” — thus Hertwig summarizes, — “the germi-
native vesicle undergoes a series of changes in that its dot breaks up into
several pieces, its membrane is dissolved, and the nuclear fluid (Kern-
saft) mixes in part with the yolk. These changes are to a certain extent
independent of each other, inasmuch as the dot may persist when the
membrane is already dissolved, and wce versa. Out of the fragments of
the nucleolus and the remnant of the nuclear fluid arises the fibrous spindle-
shaped nucleus.” Whether the accessory nucleoli, and whether the whole
or only a part of the nucleolus, contribute to this spindle is uncertain.
The migration to the periphery of the vitellus may take place in either
of the two conditions of the nucleus.
The further changes which the excluded egg undergoes within the
cocoon were traced on another genus,— Nephelis. The spindle lies
already at the time of exclusion in a radial position, with one end near
the surface. The first changes are as follows: the rods of the middle
zone (Kernplatte) elongate ; the homogeneous areas, especially the pe-
ripheral, become larger, and the surrounding rays more prominent and
extensive ; the peripheral area is visible in the living egg. Passing over
so much as relates to what may be seen on the living egg of the for-
mation of the first polar globules, I will enumerate only the internal
changes. With the formation of a protuberance of the protoplasm at
the animal pole the spindle moves farther and farther from the centre
of the egg, for its peripheral tip remains as if attached to the summit of
the elevation. The middle zone of thickenings splits into halves, which
migrate as in nuclear division generally. The granules remain united
by nuclear filaments. In consequence of this, the spindle has increased
considerably in length.* It therefore comes to lie, when the pinching
* It seems to me that the lengthening of the spindle is very inconsiderable till
near the close of the constriction which forms the polar globule, so that it is not quite
exact for Hertwig to refer the lengthening of the spindle to any of the preceding
MUSEUM OF COMPARATIVE ZOOLOGY. 439
off of the conical protuberance to form the polar globule begins, half in
the latter and half in the superficial layer of the yolk. The radiation
has meantime diminished, especially in the polar globule, where there is
_ to be seen only a very indistinct arrangement of the protoplasm around
a dark granule, the peripheral apex of the spindle.
I can only confirm for Limax this description, which agrees in every
essential particular with what I have seen. In one point, however, I
have been less successful than Hertwig. I have not seen the continua-
tion of the spindle fibres to the centre of the clear astral area. I observe,
moreover, that Hertwig has not uniformly represented the apex of the
spindle as occupying the centre of this astral area (e. g. the deep end of
the spindle, loc. cit., Taf. II. Fig. 2).
Of the lateral zones of thickenings Hertwig adds that they appear,
when viewed lengthwise of the spindle, as two circles (not rings) of shin-
ing granules. About two hours intervene in Nephelis between the cor-
responding stages in the formation of the two polar globules. The
changes transpiring during this interval, as I have elsewhere indicated,
have hitherto eluded most, if not all observers.*
This hiatus in his observations was recognized by Hertwig, for he
says (p. 27) this point —the formation of the second spindle — has
remained obscure. According to the ordinary course of nuclear division
the half of the spindle which remains in the yolk should at first be con-
verted into a homogeneous nucleus, and only then elongate. Some
of his preparations also seem to favor the justice of this conclusion ;
namely, those where the granules of the semi-spindle remaining in the
egg had imbibed nuclear fluid and formed small vacuoles. As other
intermediate stages were wanting, Hertwig did not feel able to deny the
possibility of a completion of the spindle in a more direct manner.f
phenomena, especially not to the separation of the halves of the nuclear disk. This
is at once evident, I think, from his own figures, as well as from those I have given
of Limax. Compare Fig. 40 with Fig. 43.
* It is true Fol (77°, p. 448) allows the second spindle to arise by a simple length-
ening of the half of the spindle fibres remaining in the yolk, and an elongation of the
fibre thickenings; but this conclusion may perhaps not be considered as authoritative
and final until it has been shown that intermediate stages cannot have been over-
looked. Figures of such intermediate steps as will be a certain guaranty against
mistake have not, I believe, been published. There is the more reason for not giving
his conclusions too great prominence in this matter, since he affixes so little impor-
tance to the spindle fibres, and has in the work just cited figured for the first time in
his writings their thickenings.
T It may not be quite irrelevant to notice that the intervals which here elapse
between the formation of the two polar globules on the one hand, and between the
440 BULLETIN OF THE
After the formation of the second polar globule, which somewhat ex-
ceeds the first in size, but is otherwise like, and formed like, the first,
the half of the spindle remaining in the egg contains a disk of granules,
and about its tip a homogeneous area and faint radial striations. A little
later a cluster of vacuoles closely pressed together has taken the place
of the granules of the disk. These vacuoles are sharply limited from
the yolk by a dark lustrous rind having the appearance of nuclear sub-
stance, and in the contained fluid small dark granules are suspended.
The vacuoles soon increase in size, and flow together into a simple, lobed
body, —a nucleus. This female pronucleus migrates toward the centre
of the egg, where it meets the male pronucleus. Meanwhile there have
appeared in the last-formed polar globule numerous vacuoles in place of
the granular zone which occupied its middle. These enlarge and unite
into a single vacuole with a dark cortical layer, which stains in carmine.
The first-formed globule is partially constricted into two. All three
remain attached to each other, and, through the largest one, to the yolk,
till about the time of the first cleavage, when they are all combined into
a single flattened structure containing three bodies that stain readily.
The formation of each polar globule takes place in the manner of a cell
division, or, in view of the difference in size of the products, as a cell
budding.
Hertwig’s studies on Rana are mostly confirmatory of the results
reached by Van Bambeke. In the ovarian egg at the time the germi-
native vesicle is growing most rapidly it presents a spherical form and
complicated structure. There is a membrane and about a hundred
nucleoli, which are in contact with its inner surface,* and a rich net-
work of finer or broader bands of protoplasmic substance, whose function
it is to nourish the nucleoli. The latter are most important compo-
nents of the nucleus. Already at the beginning of winter the germina-
tive vesicle is found more or less displaced from the centre toward the
pigmented pole of the egg, and, although a shrinking in the vesicle
takes place, the cavity found outside the vesicle in eggs hardened in
formation of the second polar globule and the first segmentation on the other hand,
are very nearly the same, so that the production of a ‘‘ homogeneous nucleus” and its
conversion into a second spindle cannot be excluded on account of any lack of time
for the metamorphosis, provided the changes transpire with the same rapidity as they
do in the preparation for the first cleavage.
* The nucleoli differ in chemical behavior from the nuclear membrane, with which
they do not become fused. In Hertwig’s opinion, therefore, Van Beneden’s view
that both are unaltered renmants of the primitive nucleus (i. e. ‘‘nuclear essence ”)
is not tenable.
MUSEUM OF COMPARATIVE ZOOLOGY. 441
alcohol is an artificial condition, as Bambeke maintains. The shrivel-
ling of the vesicle is accompanied by a centripetal migration of the
nucleoli. Further changes take place only in the early spring. The
vesicle then approaches close to the dark pole, and ultimately exchanges
its much lobed and folded outline for that of a flattened curved disk.
A pigment zone surrounds this disk, —in R. temporaria even on the
superficial aspect, — and is continuous with a pigment stripe extending
a short way toward the centre of the yolk. The deep end of this stripe
is swollen, and embraces a circular clear space connected with a funnel-
shaped similar space immediately under the germinative vesicle. No
nuclear structure is to be found in the circular spot. The whole re-
sults from the closing together of the pigment zone which surrounded
the vesicle when the latter migrated toward the surface, and therefore
indicates the course it had taken. The method of the ultimate disap-
pearance of the vesicle, which probably takes place about the time the
eggs are set free in the abdominal cavity, was not discovered. All the
eges from the body-cavity and the oviduct exhibit the same condition, —
the peculiar distribution of pigment matter named by Bambeke clav-
form figure, and the hemispherical clear mass of yolk at the peripheral
end of the latter, but not the least thing, within or without the yolk,
that could be considered as a remnant of the germinative vesicle. The
vesicle is not eliminated in the Amphibia, as in the trout, but is dis-
solved without recognizable remnant, and mingled with the yolk be-
fore fecundation. This takes place, however, only after the vesicle has
reached the surface.
Finally, Hertwig discusses at some length (pp. 68-71) the significa-
tion of the polar globules. The three principal sources of confusion
in their interpretation have been: (1.) an exaggerated estimate of’ the
frequency of their occurrence ; (2.) a mistaken identification of widely
different structures, in that every formed particle of protoplasm between
yolk and egg membrane has been considered polar globule ; and (3.) the
assumption of a genetic connection between two often contemporaneous
phenomena, — the disappearance of the germinative vesicle in the mature
egg, and the appearance of formed bodies outside the yolk. Since it
has been shown that the regressive changes of the germinative vesicle
and the metamorphosis of the germinative dot into a spindle-shaped
nucleus take place in the ovary a long time before the exclusion of the
egos, and that it is only after this that the formation of polar globules
takes place, it is evident that the processes stand in no relationship ;
they must be separately estimated.
442 BULLETIN OF THE
While the phenomena of fecundation are, with slight modifications,
the same in all cases studied, the process of maturation is subject, in
_his opinion, to greater variation. The simplest method of producing an~
“ego nucleus” from the germinativé vesicle is by a uniform distribu-
tion of nuclear substance in the nuclear fluid, and then by a solution of
the nuclear membrane, such as appears to take place in conifers accord-
ing to Strasburger. With animal eggs, however, the process is more
complicated, and there are three methods to consider, of which the
simplest is that furnished by Toxopneustes, where the germinative
dot persists as “egg nucleus.” With the leeches this is modified by
the intercalation of the accessory process of forming polar globules,
whereby the nucleolus, instead of becoming a homogeneous “ Eikern,”
forms at first a spindle-shaped “ Eikern,” and only indirectly the homo-
geneous nucleus. With the amphibians, finally, only a small portion
of the nuclear substance — perhaps a single nucleolus — furnishes the
diminutive nuclear structure. The last is a modification in the process
induced by the mu/ti-nucleolar condition of the germinative vesicle.
By studies on Ascaris nigrovenosa Branpt ('77) endeavors to refer
all the differences in the appearances presented by the germinative
vesicle, its supposed disappearance among others, to an amceboid nature,
which induces constant change of form. This Brandt claims can be
directly observed.
Much of the value which might otherwise attach to his observations is
lost from his not having supplemented his work with the proper use of
reagents, and from his ignoring the advantages of compression already
employed with such success by Auerbach. Brandt goes so far as to
express the opinion, that the substance of the germinative vesicle can
flow around and envelop the yolk, and that it can assume dendritic
forms, become diffuse, disappear, and again collect itself.
With regard to the nuclei [pronuclei] discovered by Biitschli and
Auerbach, Brandt, although at first incredulous, satisfied himself of
their existence ; but instead of arising as minute spots or suddenly as
clear balls, they at first present, according to him, the appearance
of indistinct, diffuse spots of irregular shape, which, with constant
amoeboid change of form, at length become rounded, and then appear
most distinct. They are not, however, bodies sw¢ generis, but rather
portions of the germinative vesicle that has become parted by ameboid
motion, and is thus reconstructing itself. The mutual approach of
these pronuclei he explains as being brought about by a change in the
position of the pseudopodia ; still the yolk may concur in this move-
-- a
MUSEUM OF COMPARATIVE ZOOLOGY. 443
ment, especially since a mutual approach of the vesicles is also to be
observed while they remain quite spherical. A third cause, he believes,
is to be sought in a contractile connecting substance stretched between
the two vesicles, in the form of a protoplasmic network, since it is ques-
tionable if the contractility of the yolk can effect a regular approach of
the vesicles (pp. 371, 379). Finally the latter are completely fused.
The germinative vesicle in the egg of the nematode is neither dissolved
nor otherwise destroyed.
Giarp ('77) gives a description of hyaline spheres which in Rhizo-
stoma make their appearance near the surface of the egg, and at its
maturity constitute a clear zone just underneath the vitelline mem-
brane. As previously (p. 332) stated, he ascribes to Biitschli the
discovery that the polar globules are formed in many animals by a
process of cell division. With all these animals the excreted corpuscles
have the value of rudimentary cells of an atavistic signification,*® and
cannot be properly called “corpuscules de rebut.” The latter name is
only appropriate for non-cellular material rejected by the vitellus which
serves for the formation of accessory organs, the vitelline membrane,
for example. It is with the latter that the hyaline vesicles in Rhizo-
stoma are to be classed.
The results reached by Giarp (’77*) in studies principally on the eggs
of Psammechinus miliaris confirm in many points the observations of
Fol; in others, his conclusions are different. I shall notice especially
their disagreements. The egg of this sea-urchin possesses a very delicate
vitelline membrane even before fecundation. A little before maturity the
germinative vesicle presents the reticulum characteristic of old nuclei.
The nucleolus embraces an irregular nucleolinus. The contents of the
vesicle become mingled in an amceboid mass, attain the surface of the
yolk, and there are converted into a karyolytic figure. The aster di-
rected toward the centre of the egg very rapidly assumes the form of a
rounded nucleus, — the structure O. Hertwig took to be the germinative
spot. It cannot be the “spot,” for it always appears a little smaller than
the latter, and moreover one often encounters eggs in which this Wag-
nerian spot is no longer visible, and in which the female pronucleus does
not yet present a distinct nuclear aspect. On the other hand, it is inex-
act to say that there is no genetic connection between the two (Fol), since
the substance of the nucleolus, mingled with that of the germinative
vesicle, serves for the formation of the first amphiaster, which gives rise
to the female pronucleus. Giard describes the formation of two polar
* See also Giard ’76.
444 BULLETIN OF THE
globules in non-fecundated eggs soon after their exclusion (less accurately
to be traced before exclusion). In the living eggs one sees two eleya- —
tions (cumuli) of clear protoplasm, often, though not always, at diametri-
cally opposite points of the surface of the yolk. One arises at the expense
of the aster which is fellow to that from which arises the female pronu-
cleus. This aster forms an inequal karyolytic figure, of which the small
aster becomes the cumulus which produces the first polar globale; the
second arises subsequently ; both are very small, and disappear quickly,
In using staining reagents one finds ¢wo nuclei at this pole of the egg.
The more superficial is the one which by dividing forms the polar glob-
ules; the other is the female pronucleus. This method of the forma-
tion of polar globules is, so far as I know, quite unique.
The results published by Fou (’77°) in his paper “Sur le Commence-
ment de |’Hénogénie chez divers Animaux,” have been in part given
already in the reviews of his preliminary notes. When he says (p. 441)
that the internal half of the first “amphiaster de rebut” remaining
in the yolk becomes a complete amphiaster, one might possibly be im-
clined to infer from the statement that there was some evidence of the
conversion of the internal half of the “nuclear plate” into a veritable
nucleus as one of the steps in the process of the formation of the second
archiamphiaster. This view, however, is entirely unsupported by what —
follows. In fact Fol seems to leave no chance for the possibility of such
an event, for he says distinctly in this paper (p. 448): “Then the im
terior aster is converted into an amphiaster in the following manner.
Biitschli’s filaments, instead of retiring toward the centre of the aster,
elongate anew, and the varicosities disappear by being drawn out. These
filaments again constitute a spindle (Fig. 7), one extremity of which is
found at the centre of the internal aster, while the other point of conver-
gence for the filaments corresponds to the point of contact of vitellus and
first polar globule. In the middle of these filaments new varicosities are
formed.” There is nothing in the figure cited, nor in any other of those
given by Fol, which fully warrants the name amphzaster, since no trace
of a radial influence at the outer pole of the second spindle, save the
spindle fibres, is visible, to say nothing of a complete aster at this point.
A complete spindle is present ; a complete amphiaster is not.
On another point Fol gives (p. 447) somewhat more extensive informa-
tion than hitherto. He still insists that with the starfish the first am-
phiaster does not give rise directly to the polar corpuscles. “If,” he
says, “one treats an egg with reagents a few minutes after the first am-
phiaster is formed, one no longer finds an amphiaster, but a compact
MUSEUM OF COMPARATIVE ZOOLOGY. 445
body with stellate contour. Does this body correspond to the whole
amphiaster, or to only one of its halves? Does it result from a conden-
sation or from a division of the amphiaster? The second supposition
would appear a priorz the more probable ;* but as I have never suc-
ceeded in seeing at the side of this stellate body another aster, I prefer
to adhere [?| to the first supposition.” My criticism of the assumption
first suggested by Fol — a dwision of the first amphiaster — is perhaps
intelligible in the light of his first description. With this statement of
facts, it no longer serves as an explanation. I am, nevertheless, still
unable to accept the conclusions which Fol has reached on this point,
and believe that the phenomena are to be otherwise explained than by
assuming that either a division or a temporary consolidation of the first
amphiaster normally takes place. Without personal experience with
the animal under consideration it is fruitless to attempt any explana-
tion. Possibly Fol may have been less certain than he supposed of the
relative degrees of advancement presented by the stages compared, and
that, after all, the unique stellate body may have represented a condi-
tion antecedent to the first amphiaster, rather than subsequent to its
formation. The possibility of such an error is not, in view of the
necessary use of reagents, entirely improbable. The failure of other
observers to distinguish any corresponding stage in the metamorphosis
gives reason to think this may be due to an abnormal condition of the
eges in which it was seen.
Tn living eggs, when the polar globule begins to detach itself, the sur-
face of the yolk forms folds arranged like the rays of a star whose centre
is the peduncle uniting the globule to the vitellus. These folds become
more prominent as the globule detaches itself, and then fade away. This
and other phenomena — the elevation of a distinct pellicle in the forma-
tion of the polar globules — the author thinks are easily explained, if one
admits that the superficial layer of the yolk has a greater consistence
than the yolk itself. Although this layer in certain respects deports
itself like a true membrane, in his opinion it is not such.
There result from the internal half of the second archiamphiaster one
or two small clear spots, which present, when treated with reagents, the
aspect of young nuclei. They increase in size as they sink into the yolk,
and become fused together. Other clear spots appear at the'side of the
| first, and they too are fused with it to form the female pronucleus.
/ Fol also reports the discovery of one (if there are two, the second has
| escaped observation) polar globule in the sea-urchin. They are elimi-
|
* It is the opinion previously adopted. See p. 436.
4
i ’
nated while the eggs are still in the ovary, and are formed as in the star-
fish, with the exceptions as to number and as to their failure to raise
any sort of a pellicle. On account of the absence of-a pellicle they are
soon lost after the exclusion of the egg.
The errors of Van Beneden and O. Hertwig relative to the fate of the
germinative vesicle are due, in his opinion, to the use of slight pressure,
resulting in abnormal phenomena. Other cases (Sagitta and Phallusia)
are cited to show that the vesicle may early disappear.
In Phallusia the “testa cells” arise within very young eggs and in
contact with the nucleus, but this is in no way to be compared with
the formation of polar globules, so that the sea-urchin is the only animal
whose eggs part with their polar globules while still within the ovary.
In Heteropoda after the disappearance of the Wagnerian dot there ap-
pear two centres of attraction at the two extremities of the vesicle. The
rays of the stars, which announce the existence of these centres, extend
partly without and partly within the vesicle. The latter encounter and
unite with each other, beginning with those in the middle [axis of spin-
dle?], to form the bipolar filaments of the first amphiaster. After the
second polar globule is formed, the varicosities of Biitschli pertaining to
the last aster reunite with the central mass of the aster to constitute the
female pronucleus. The male only makes its appearance when the sec-
ond polar globule is forming, notwithstanding fecundation is effected in
the oviduct long before. It is at first very small, extremely refringent,
and located at the surface of the yolk in a position variable as regards its
relation to the polar globules. In the starfish the male aster also re-
mains latent up to the same moment. At a certain stage in the growth
of both pronuclei there appears a minute nucleolus. The nucleus of
the fecundated egg has only a very remote connection with the germi-
native vesicle.
The figures given by Branpr (77°) to illustrate the formation of the
polar globules in Lymnzus cannot be considered as giving a very com-
plete idea of the process. In the author’s opinion (p. 591) the globules
are formed by a part of the ameboid germinative vesicle swelling forth
in the form of a clear rounded drop in which an irregularly outlined nu-
cleus at once appears. It is only a portion of the germinative vesicle
which is thus expelled, the most of it returning as an ameeboid body into
the vitellus, where it becomes indistinct, but still persists, to give origin
to the nuclei of the first spheres of segmentation. Brandt’s views of the
amoeboid nature of nuclei are elsewhere discussed.
O. Hertwic (77%) gives in a preliminary paper the results of studies
446 BULLETIN OF THE
_ MUSEUM OF COMPARATIVE ZOOLOGY. 447
on the eggs of a number of animals made in the early part of the win-
ter of 1876-77, —therefore very nearly contemporaneous with Fol’s
valuable investigations. As the ultimate illustrated papers (Hertwig,
"78 and "78"), giving more fully the results on which this preliminary
communication is based, have already appeared, I will limit myself
here to a statement of Hertwig’s general conclusions, and refer the
‘reader for details to the review of those papers which will be found
_ farther on. é
ie ‘Hertwig has also discovered, independently of Fol, the existence of
polar globules * in Sphzrechinus brevispinosus, which were formed in
this case from eggs artificially removed with the ovarium and laid for
some time in sea-water. From all his observations Hertwig finds
‘confirmation of his previously expressed views on maturation and fecun-
dation, especially in three points: (1.) that the continuity in the
__generations of nuclei is not interrupted ; (2.) that the polar globules
arise by a process of cell budding; and (3.) that fecundation depends
‘on the copulation of two nuclei. On the other hand, his opinion in
Weoard to the prevalence of polar globules is altered. He now believes
that a general agreement in this matter throughout the animal king-
dom will be established. The most important objective communication
in this paper is unquestionably the description given of the method in
Phich the first maturation spindle arises in Asteracanthion (see p. 452).
_ According to P. Mayer (77, p. 199) the germinative vesicle disap-
ears, in the case of Pagurus, while the egg is still in the ovary, so that
hen freshly deposited it is “positively enuclear.” Of this he has
nvinced himself by crushing the eggs, and has also often observed the
origin of a new nucleus. Before it perishes the vesicle is sometimes
to be seen near the surface of the egg, — instead of the centre, where
it always is at first, surrounded with its protoplasmic area. This
| eccentric position he regards as probably abnormal, and indicative of
| an approaching disintegration of the egg. With the disappearance of
| the vesicle the protoplasmic area surrounding it ceases to exist. For
| this reason a direct dispersion of the elements of the vesicle in the pro-
_toplasm is the simplest assumption. The protoplasm, retaining its net-
like distribution, may subsequently secrete a new nucleus in its centre.
Since the existence of a distinct egz membrane (not affected by caustic
potash) and of the germinative vesicle appear to exclude each other ;
and since fecundation must precede the formation of the membrane, Kg
_* The existence of polar globules in the sea-urchins was established by Agassiz
| in 1867. See A. Agassiz, '64, p. 6, Pl. I., 77, Daiseelt. cand ‘GF, ps2.
448 BULLETIN OF THE
concludes that the vesicle disappears after fecundation, whether as a
result of fecundation is uncertain (p. 204). Mayer seems also to have
seen in isolated cases of freshly laid eggs a “sort of Richtungsblischen —
in process of elimination” ; but he considers this process as also abnor-
mal, so that his subsequent suggestion, — that it were, perhaps, not too
venturesome to connect this with the eccentric position of the germina-
tive vesicle, —has not that importance in his mind which can fairly be
attributed to it to-day. |
StossicH ('77) has extended his observations to the Hchinoderms,
and maintains the same view relative to the morphology of the egg
which he previously expressed (76). The germinative vesicle of the’
egg mature and ready for fertilization has a perfectly spherical form,
but no membrane; its protoplasm is clear, transparent, homogeneous,
and slightly granular. He does not know that Hertwig’s observations
of a delicate network within the germinative vesicle have been con-
firmed. If it had so complicated a structure, it could no longer be
regarded as a cell, but as a much more differentiated organism. The
germinative dot always has an eccentric position, is round, and contains
a very well pronounced nucleolinus. The author says he has several
times had the opportunity of seeing two germinative dots in a single
egg. They were, however, always joined ; in these cases the nucleolini
were wanting.
I do not doubt that these two “germinative dots” are really the
conjugating pronuclei, although the accompanying figure (oc. cdt., Tay.
I. Fig. 2) gives no evidence of the existence of polar globules or the
elevation of the membrane of the egg at any part of the periphery
which is shown.
After fecundation the nucleolinus is no longer visible, and the con-
tours of the dot become always less decided, until they disappear with-
out leaving a trace. The vesicle from being round assumes an irregular
dentate outline. This change of form is only the effect of a movement
developed within the egg by reason of contact with the sperm.
Stossich desires his previous hypothesis, that the germinative vesicle
approaches the surface in consequence of the greater density of the
external layer of the yolk, to be so far corrected as to grant that this is
aided by the amceboid motion of the vesicle. He is unable to say
whether the whole ‘of the vesicle escapes as the two or three directive
vesicles. After the elimination of the last polar globule the yolk be —
comes homogeneous, then there is in its centre, after a little time,
a round body which becomes more distinct. It is the nucleus of the |
9
MUSEUM OF COMPARATIVE ZOOLOGY. 449
first ‘“‘embryonic sphere,” — the analogue of the germinative dot. Its
contour at length becomes less distinct and it entirely disappears.
With the dissolution of the nucleus the existence of the first embryonic
sphere is at an end, although some minutes later there begin to be
developed in the yolk certain phenomena which lead to the formation
of two new nuclei and to the division of the yolk into two embryonic
_ spheres. The yolk is now homogeneous. Little by little a protoplasmic
mass is collected in the centre ; this increases and becomes more readily
visible, but its contours are blended ; the granules cease their rotation
and are disposed in rays. The central body becomes elongated in a
plane perpendicular to that of the polar globules; the motion is not
ameeboid ; this nuclear body is divided by a constriction, and afterwards
the yolk suffers the same fate.
Burscaui (77°, pp. 232 — 237, Taf. XVII.), independently of the recent
observations of Hertwig and Fol, radically modified his opinion of the
nature of the polar globules. In Neritina fluviatilis he finds that both
_ the fertile and the znfertile eggs of a capsule produce polar globules ; the
former at least three (only one observation), the latter a larger number,
sometimes as many as five. It is not possible, he says, to be certain that
all the globules are observed, since in opening the capsule they may
easily be lost. Staining in Beale’s carmine and the subsequent well-
known method of decoloration by means of hydrochloric acid furnishes
evidence that the polar globules are not composed exclusively of nuclear
substance, but that they are each composed of protoplasm which encloses
from one to three small nucle: ; and, further, that the infertile yolk after
the formation of the polar globules still embraces from one to three
small nuclei,—#in other words, that a part at least of the germinative
vesicle remains in the yolk after the production of the polar globules.
Biitschli fully accepts O. Hertwig’s view of the origin and nature of
the polar globules, but still from a physiological standpoint thinks their
principal signification is to be sought in the removal of a portion of
the egg nucleus (germinative vesicle), whether this is accomplished
directly or under the form of a “ Zellknospung.”
It is probable, he adds, that the infertile eggs have remained unfe-
cundated. If this be true, Neritina will afford evidence that polar
globules may be produced by unfecundated eggs, a conclusion which
Fol and Hertwig have likewise reached from satisfactory evidence. In
view of their extensive prevalence, the polar globules are probably of
fundamental significance ; their import will receive a sufficient explana-
tion only with a more intimate knowledge of the processes of reproduc-
VOL. VI.— No. 12. 29
se
450 BULLETIN OF THE
tion — especially the phenomena of conjugation—among the lower
organisms.
A critical review of Biitschli’s “Studien,” etc., by DaLumncER anp
DRYSDALE (77), is principally directed to pointing out what is obser- —
vation and what inference in Biitschli’s work.
HatscHek (77%), without having devoted especial attention to the
phenomena of maturation in Pedicellina echinata,. has observed (p. 504)
the existence of two or three (?) polar globules of variable size, which
are found at the animal pole of that axis which he believes is differen-
tiated in the unsegmented eggs of all Metazoa (p. 524). A definitely
limited nuclear structure nearer the animal than the vegetative pole
(which may be the primary cleavage nucleus) is the centre of a radial
arrangement of the yolk elements.
The maturation changes of the eggs of Malacobdella and Clepsine
have been incompletely observed by Horrmann (77, pp. 18-21, and
77", p. 34). In the former case the germinative vesicle in approaching
the surface gradually diminishes in size, but preserves its rounded out-
line. ‘Two hours after fertilization two polar globules were seen.
With the growth of the egg of Toxopneustes variegatus there appears
according to SELENKA (78 and "78“) a remarkable differentiation of the
cell into three concentric layers. The middle is a very thin pellucid
layer of protoplasm without granules, and disappears when the full size
isreached. During the later stages of growth, the outer yolk layer sends
out pale pseudopodia, which, at first isolated, arise as blunt or bush-like
projections of rapidly altering form, but finally assume the shape of very
numerous and fine, motionless rays. These, he believes, serve for the
growth of the egg. The whole yolk is undergoing change of form dur-
ing the activity of the pseudopodia. Finally it comes to rest, and the
pseudopodia are withdrawn. Meantime the germinative vesicle has suf
fered changes from its spherical form ; its membrane has been variously
folded and wrinkled ; it has approached the periphery of the yolk after
the resorption of the germinative dot. Two polar globules are formed.
The place of their formation remains a long time recognizable as an
elevation of the surface of the yolk (Dotterhiigel). There then appear
in the yolk under this elevation several clear bodies which unite to form
the “Eikern.” The latter moves inward, but does not take a central
position in the yolk. It is probable that the “clear bodies” are the
product of a budding (Abschniirung) of the germinative vesicle.
The comparison which StrasBuRGER previously ventured to draw be-
tween polar globules and the “ Bauchkanalzelle” of the higher crypto-
|
—
MUSEUM OF COMPARATIVE ZOOLOGY. 451
gams and archisperms, makes it of considerable interest to learn the
conclusion which he reaches in his more recent studies (Strasburger "77)
on the ‘‘ Embryosack” of metasperms. The whole process within the
embryo-sac (studied especially in Orchis) is put in a new and unequiv-
ocal light. The egg cell, the two “companion cells” (Gehiilfinnen),
and the “antipodal cells” (Gegenfiisslerinnen) are all formed, not by
a free cell-formation, but by the successive divisions of the cell which
forms the beginning of the embryo-sac, and with each division the
nucleus undergoes a spindle metamorphosis. From these successive
divisions there result eight cells, four in each end of the embryo-sac, or
more properly speaking eight nuclei, only six of which (three at each
end), become definitely circumscribed cells, since the division is in so far
incomplete, that one of the four nuclei in each end of the embryo-sac
is left free in the protoplasm of the sac not employed to form the six
definite cells. The two nuclei thus left free migrate toward each other
and fuse (conjugate?) to form a single nucleus. The group of three
cells at the posterior end of the sac are the antipodal cells; of the
anterior group, two are the “companion cells,” whose anterior ends form
the “ Fadenapparat”’- when it exists, and the remaining one is the egg
cell, whose sister nucleus was the anterior of the two copulating nuclei.
The “companion cells” cannot be considered equivalent to “canal
cells” (or polar globules), since they are not derived directly from the
egg cell. The “free” nucleus is the one last to be separated from the
nucleus of the egg cell, but its entirely anomalous fate prevents any
comparison with canal cells, or, for that matter, with any other, save
copulating sexual cells.
For the present, then, the angiosperms seem to present no opportunity
to extend our knowledge of the possible origin of the polar globules.
Notwithstanding this there still remain these important facts, to which
Strasburger directs attention, since they show that often parts of the cells
which are undergoing sexual differentiation are detached at early stages,
and are excluded (like polar globules) from the subsequent sexual act:
that in Spirogyra Heeriana a vesicular portion of the cell, which at the
time of copulation migrates, is excluded from the copulation (in other
Spirogyras, however, this is not the case); that in certain alge, for in-
stance, a part of the egg substance is simply ejected, and also that not
all of the substance of the antheridium is employed in the formation of
the spermatozoids; that in higher cryptogams the “ Bauchkanalzelle” is
formed, and the spermatozoids carry about for a time a vesicle which
represents a part of the “ Mutterzelle” and which is in no way con-
452 BULLETIN OF THE
nected with the fecundation ; and finally, that in the archisperms an
equivalent of the “ Bauchkanalzelle” is formed, and that perhaps the
separation of the contents of a ‘vegetative cell” in the pollen grains of
-archisperms has a preparatory significance for the formation of fecundat-—
ing substance. But a difficulty in the way of this view for the spermato-
zoids of archisperms is the fact that in Selaginella and other Dichotomese
both the “ vegetative cell” and the “ vesicle ” are present.
Before the maturity of the egg of Asteracanthion, there is, says
O. Hertwie (78), a migration of the germinative vesicle toward the
surface of the yolk, where it loses its intra-nuclear network, and where
its membrane becomes uneven by reason of infoldings. He recognizes
that the germinative dot is composed of two substances, which differ
both in the fresh condition and more emphatically when treated with
reagents. The smaller portion lies as a protuberance on the larger, or
may be entirely surrounded by the latter; it is more promptly and
deeply stained, and resists the swelling influence of ammoniacal fluids
longer, than the larger portion ; the latter becomes in 2—4% acetic acid
quite transparent, while the former becomes intensely lustrous.
The changes at the time of maturation are inaugurated in the proto-
plasm which surrounds the vesicle. In the living egg it is seen that a
knob (Hocker) of protoplasm pushes its way into the germinative vesicle
from the side which lies nearest the surface of the yolk. The apex of
the knob embraces a light spot free from yolk granules, and sends out
long protoplasmic projections in all directions. The nucleolus now
(fifteen to twenty minutes after the eggs are brought from the ovary
into sea-water) loses its several vacuoles and thus appears homogeneous;
in a short time there arises in its centre a larger single vacuole, that
is nearly filled by a solid round body, which by the use of reagents is
shown to be the same as the above-described smaller portion of the nu-
cleolus. Suddenly this vacuole with its contained corpuscle disappears.
What becomes of the corpuscle is shown only by employing reagents.
The observed stages probably follow each other in this order: the
corpuscle lying in the vacuole elongates, becomes pear-shaped, then
club-shaped, at length more rodlike, and finally a series of beadlike en-
largements. It has thus come to project with its smaller end through
the rind of nucleolar substance surrounding the vacuole, and its extrem-
ity is at last found to extend into the protoplasmic knob and to occupy —
the centre of its stellate figure, This is accomplished in the course of
about ten minutes. Then there appear in the centre of the stellate
figure granules which consist of nuclear substance and are probably de-
MUSEUM OF COMPARATIVE ZOOLOGY. 453
tached from the metamorphosed rodlike body, for the latter ultimately
disappears entirely by this process. The granules assume a circular
arrangement (I will speak of them as the circle of granules). Hertwig
is unable to say positively whether the whole of the other (larger) por-
tion of the nucleolus remains in the germinative vesicle, since many
preparations favor the view that particles of this portion now make
their way into the homogeneous spot of the protoplasmic knob. It at
least finally diséppears, as does also the membrane and later the
“ Grundsubstanz” of the germinative vesicle.
What becomes of the “ circle of granules” Hertwig unfortunately does
not state ; also the origin of the second stellate figure and the spindle
fibres that unite them cannot be considered as satisfactorily explained
by these observations.
During the disappearance of the smaller nucleolar body, as seen in
living eges, and soon after the début of the first small radial figure, there
appears a second like figure near the first. In using acetic acid it is
seen that there lies between these two stellate figures a fibrous body
whose fibres become more distinct as the remnant of the nucleolus disap-
pears. This body ultimately forms the ‘‘Richtungsspindel.”” The latter
elongates and takes a radial position, while the asters increase in size.
Just what relation the “circle of granules” sustains to this spindle,
I am unable to discover. It is a difficult point that needs to be defi-
nitely settled. Perhaps the conclusion nearest at hand is that the jibres
of the spindle are formed from the outer and larger part of the nucleolus;
that the znner corpuscle of the nucleolus furnishes directly, in the ‘‘circle
of granules,” the equatorial zone of thickenings. But apparently irrec-
oncilable with this supposition is the fact that the “circle of granules”
occupies the centre of the first star, and that the second star arises near
(not by a division of) the first.
The more general conclusion,* and one of fundamental importance,
which Hertwig reaches in his preliminary paper ('77% p. 273), seems in
the main just, and it is greatly to be regretted that he was not able to
* “Wenn ich die geschilderten Befunde deuten soll, so scheint mir ein unverkenn-
barer Zusammenhang zwischen dem Auftreten der beiden Strahlensysteme und der
& Umbildung des Keimflecks der Art zu bestehen, dass bei der Auflosung des Keimbliis-
chens die Kernsubstanz in das Protoplasma iiberwandert und an dem Orte, wo sie
‘sich zu dem Spindelformig differenzirten Kern ansammelt, erst ein und dann das
zweite Strahlensystem hervorruft. In erster Linie ist bei dieser Umlagerung der ac-
tiven Kerntheile der in der Vacuole des Keimflecks eingeschlossene kuglige Kérper
betheiligt. Aber auch von der einhiillenden Kernsubstanz genet offenbar Theile,
wenn nicht Alles, in das neue Kerngebilde mit iiber.”’
454 BULLETIN OF THE
settle at the same time the nature of the share each of these nucleolar
structures takes in the formation of the maturation spindle. There is,
besides, one important point which is not, even in these studies, made
sufficiently clear to satisfy me. Iam unable to understand how the sub-
stance of the nucleolus is more active in producing the stellate figures
than the protoplasm of the yolk. If this radial system is induced by
the immigration of nucleolar substance into the protoplasmic knob, then
certainly we should not expect the stellate figure before such immigration ;
consequently the question must arise, What is the signification of the
clear non-granular spot in the protoplasmic knob? Is it not due to the
same agency as that which induces the stellate figure? Is it not, in
fact, simply the first trace of such a figure still limited in its extent?
But this clear spot antedates even that part of the metamorphosis of
the nucleolus by which its several vacuoles are succeeded by a single
larger subcentral vacuole embracing the smaller nucleolar body (compare
Hertwig, "77%, p. 271) ; by so much the more, then, does it antedate the
conversion of that smaller nucleolar corpuscle into a rodlike body with
its end at the centre of the star. And, further, what shall be said of the
“langgestreckte Protoplasmaerhebungen,” ‘‘ which are sent out in the
upper wall of the germinative vesicle, raylike, from the apex of the proto-
plasmic knob on all sides, like mountain ridges from a central peak”?
They are represented in Hertwig’s Taf. VI. Figs. 2 and 3, at a time when
the inner corpuscle is entirely enclosed in the vacuole of the nucleolus,
and yet the peculiar radial arrangement of these ‘ Erhebungen” can
hardly be due to any other cause than that which induces the stellate
figure. If the first indication of the commencing metamorphosis is seen
in the invasion of the territory of the germinative vesicle by a protuber-
ance of the surrounding protoplasm, what can be the necessity of trans-
ferring the initiative activity to the nucleolus, which still preserves its
morphological integrity? May it not be that Hertwig, by his commend-
able exertions in rescuing the nucleus from a position of comparative
subordination, has ascribed to this substance undue importance, and
given it exclusive control where it is, after all, only one of two co-ordinate
factors? A connection there doubtless is between the metamorphosis of
the germinative dot and the formation of a nuclear spindle, but it is not
so certain that the nuclear substance gives the first impetus to the forma-
tion of the stellate figures, which mark, in some cases at least, the first
unequivocal steps toward a spindle metamorphosis. When Hertwig
speaks of an ‘‘ Ueberwanderung” of nuclear substance into the proto-
plasm, I understand that to imply —as in fact his figures in so precise
MUSEUM OF COMPARATIVE ZOOLOGY. 455
and satisfactory a manner indicate —a transmigration of recognizable
morphological fragments of that substance. If, on the other hand, one
were to maintain that dissolved portions of the nuclear substance first
escaped the limits of the nucleus (and germinative vesicle), and then
were re-collected and thus gave the initiative to the protoplasmic asters,
it would be as impossible, with our present means of investigation, to
refute as to prove the claim.
A short pause ensues — to return to Hertwig’s description — after the
formation of the first maturation spindle. The formation of the polar
globules follows as in Nephelis. Two points only are of further interest :
first, that Hertwig noticed furrows on the surface of the polar globule,
as well as of the egg, which converged toward the place of constriction
during the budding process, and that the spindle before the formation of
the globules becomes broader and shorter.
The possibility of an indirect formation of the second maturation
spindle, which Hertwig emphasized on a former occasion, neither finds
support nor opposition here. The fact that the inner aster has been
converted into a “Doppelstrahlung” within a quarter of an hour after
the formation of the first polar globule, would seem to preclude the
possibility of such an event in the case of the starfish. Nevertheless, I
think this point is worthy of still further examination.
A zone of granules occupies each of the polar globules; a third, says
the author, lies near the surface of the yolk. From the latter is formed
_ the egg nucleus, —just how is not quite evident. In the clear space which
these granules occupy there appear later a number of vacuoles, and in
the centre of each a granule of nuclear substance. The vacuoles soon
become confluent, thus forming the egg nucleus, and later the granules
are united into a single structure,* —the nucleolus. The egg nucleus
has moved during its formation toward the centre of the egg. Hertwig
does not say whether the stellate condition which the protoplasm “ nach
dem Centrum des Eies zu” has assumed goes in advance of the vacuole
or not. It ultimately becomes fainter, and disappears. Hertwig did
not succeed in verifying Greeff’s observations of the parthenogenetic
development of the starfish.
Capers (78, pp. 438-447) has ascertained that, accompanying
the metamorphosis of the Ammocetes stage into the adult form of Pe-
tromyzon Planeri, the germinative vesicle of the ovarian egg undergoes
a very slow migration to the surface of the yolk, and a metamorphosis
* In the preliminary paper ('77%, p. 274) it is stated that a single nucleolus arises,
after the vacuoles have become confluent, by an ‘‘Ausscheidung.”
456 BULLETIN OF THE
from which an egg nucleus (in Hertwig’s sense) arises. The stages of
this metamorphosis are not very completely known. Eggs taken between
the middle of October and the middle of November from animals ap-
proaching maturity exhibit the germinative vesicle, still sharply outlined
and already arrived at the periphery of the yolk. Those taken toward
the end of November and at the beginning of December, on the contrary,
show that the vesicle has already lost its germinative dot and its sharp
contour, and only its protoplasm lies in an irregular form at the periph-
ery. Within this mass of protoplasm are observable, in the fresh state
of the egg, “all sorts of nuclear structures,” which are probably descend-
ants of the germinative dot. In many eggs, however, — and these the
largest in the ovary, — there was nothing to be seen of a germinative
vesicle or nuclear structures ; there was only a clear drop of protoplasm
at one point of the periphery. Already, on the 9th of December, the
eges of a completely metamorphosed larva exhibited a new nucleus
(Hikern) in this clear mass of protoplasm or remnant of the germinative
vesicle. Calberla thinks, without having recorded any direct observa-
tions of such an act, that a part of the vesicle is eliminated as the polar
globule. The new nucleus then migrates toward the centre of the egg,
drawing after it a cord of protoplasm destitute of yolk granules. Thus
a month or more before the maturity of the egg one finds the following
complications of structure. The egg membrane is thickened and exhibits
a micropyle at its narrow end where the germinative vesicle approaches —
the surface; this he calls an owter micropyle, to distinguish it from the
entrance to a canal — “ Spermagang”’ — formed directly underneath it in
the granular yolk by the centripetal migration of the egg nucleus and
the clear protoplasm it carries with it. The entrance to this latter canal
is the inner micropyle. Protoplasm which is destitute of granules en-
velops the granular yolk on all sides, and is thickened at this, the animal
pole, where it is continuous with the likewise clear protoplasm that fills
the “Spermagang.” Within the enlarged deeper end of the latter the
egg nucleus lies surrounded on all sides by a stratum of this clear pro-
toplasm.
GaLeB (78%, pp. 363-366, Pl. XXII. Figs. 1-4) maintains, on
much the same ground as the embryologists of ten and twenty years
ago, that the germinative vesicle persists, and (without any fibrous meta-
morphosis) undergoes a simple elongation, constriction, and ultimate di-
vision to form the unequal nuclei of the first pair of blastomeres.* He
seems to have taken no measures to insure himself against the possibil-
* See also the review at p. 334.
MUSEUM OF COMPARATIVE ZOOLOGY. 457
ity of committing the same mistake as the earlier writers, who con-
cluded that the germinative vesicle divided because they saw a nuclear
structure (which we now know is ot the germinative vesicle) undergo
such changes as are here reported. The observations of stellate figures
on living eggs are too numerous to allow the acceptance of his con-
clusion that they are due to the use of reagents. The figures given by
Galeb are interesting in several particulars. His Fig. 3 (Pl. XXIL.)
probably shows the pronuclei, which Biitschli figured four or five years
ago in a similar situation. Whether it is the germinative vesicle or the
female pronucleus which is shown in Fig. 1, it is noticeable that the
structure is not in such a position as to warrant the supposition that
the polar globules are produced at the equator of the egg, where the
first cleavage plane occurs. The position of the globule after its libera-
tion would, of course, be of comparatively little value in determining
this point, because of the possibility of its passively being made to
occupy a position different from that which it had when first produced ;
in the case of the female pronucleus or germinative vesicle, however,
such a displacement could not be assumed. If future observations
directed to settling this point —the mutual relation of the first cleavage
plane and the polar globule at the time of its formation — shall show
that in some nematodes the globule is formed at the pole of the egg, and
that the segmentation plane passes through the equator, it will be nec-
essary to seek some explanation of this variation from what now seems
to be a very general law. ‘The possibility of a rotation of the yolk after
the formation of the polar globules, so that the pole of the yolk comes
to occupy the equator of its shell, is not to be lost sight of in this
connection.
Batrour (78%), after giving a concise account of recent progress in
the study of the maturation of the ovum, states some conclusions which
he thinks already warranted by the observations (pp. 120-124). The
peculiar changes which the germinative vesicle undergoes at the time
of maturation are, in part at least, of a retrogressive character. The
budding of the polar cells is entirely independent of impregnation. He
says further, “I would suggest that in the formation of the polar cells
part of the constituents of the germinal vesicle which are requisite for
us functions as a complete and independent nucleus * are removed to make
room for the supply of the necessary parts to it again by the spermatic
nucleus.” From the probable absence of polar cells in cases where par-
thenogenesis is most common, he is led to suggest further, “ that a more
* The original is not Italicized.
458 BULLETIN OF THE
or less essential part of the nucleus 1s removed in the formation of the polar
cells ; so that in cases, e. g. Arthropoda and Rotifera, where polar cells are
not formed, and an essential part of the nucleus not therefore removed, par-
thenogenesis can much more easily occur than when polar globules are
formed.”
“Tt is possible,” Balfour further observes, “that the removal of part
of the protoplasm of the egg in the formation of the polar cells may be a
secondary process due to an attractive influence of the nucleus on the
cell protoplasm, such as is ordinarily observed in cell division.”
RepiacHorr (’78, p. 412, Figs. 1-10) gives a brief account of the
structure of the germinative vesicle and some of the changes which
overtake it in the case of Tendra zostericola, but reserves an extended
account for a future occasion, when his observations shall have been
concluded. In the black, round ovarian eggs the vesicle possesses a dis-
tinct membrane ; the germinative dot is of irregular form and embraces
several irregular vacuoles. When the egg has assumed its peculiar bi-
lateral form the vesicle still retains its membrane, and there is then to
be found in stained eggs within the germinative vesicle a single, or
sometimes two nucleoli, and other spots less deeply stained than the
nucleoli, but more deeply than the nuclear fluid. Sometimes it was
impossible to find evidence of the existence of a germinative dot in any
form. He only hints at the possible fate of the vesicle, and then calls
attention to the existence of two polar bodies (“ Excretkorperchen ” ?)
differing considerably in size, which were observed in the plane of, and
just prior to, the first segmentation.
The peculiar growth and activity of the egg of Toxopneustes variega-
tus has already been given. SexenKa (’78*) adds in the present paper
that in the germinative dot there arise vacuoles, which appear to lead to
its complete dissolution ; of this, however, he is made doubtful by the
different results obtained by O. Hertwig. He is in accord with Fol and
Hertwig as regards the formation of polar globules by the division of a
spindle and the re-formation into the “ Eikern” of so much of the latter
as remains in the yolk. It is perhaps doubtful if “ pronucleus” is in a
morphological sense a proper expression, since neither sperm nucleus
nor egg nucleus can alone play the réle of a cell nucleus.
While the polar globules emerge, a drop of protoplasm free from
granules flows out and soon envelops the whole yolk in the form of a
cortical layer endowed with automatic motion. Its fate is threefold :
(1.) its outer limiting layer is afterwards elevated as a vitelline mem-
brane ; (2.) a part penetrates with the spermatozoon into the “ clear
MUSEUM OF COMPARATIVE ZOOLOGY. 459
area” of the first vitelline “sun” (though often observed, this is
thought by the author to be without significance) ; but (3.) the greater
portion is drawn into the segmentation cavity during the beginning of
cleavage, where it helps to form the ‘‘ Gallertkern.” The ‘“ Dotterhiigel ”
remains, and with some exceptions the plane of the first segmentation
passes through it.*
The author agrees with Fol that the vitelline membrane is not pre-
formed, but arises with the penetration of the first spermatozodn, and
thus offers an insurmountable obstacle to the penetration of other
spermatozoa.
KupPFFER UND BrEnecke (78, p. 21) maintain that in the case of
Petromyzon Planeri and P. fluviatilis there are two polar bodies (Rich-
tungskorper) eliminated, one before and one after fertilization. As re-
gards the former of these, it was first observed after the retraction of
the vitellus,f and therefore its origin and the method of its formation
were not observed. It was entirely overlooked by both A. Miiller and
Calberla. Kupffer and Benecke say (p. 16) that it gives the impression
of a nucleus which is surrounded by a small portion of a coarsely granu-
lar mass. Often a distinct nuclear membrane is to be seen, and some-
times within it a highly refringent nucleolus ; more often, however, only
fragments of a nucleolus. They think it comes from the substance of
the disappearing germinative vesicle, either before or during fecundation.
It is applied to the inner surface of the watch-glass-shaped elevation of
the egg membrane,f but never at the highest point of the dome; and
when the micropyle is eccentric, it is found on the side of the dome
opposite the latter. The authors combat the view entertained by Cal-
berla, that the germinative vesicle gives place to a female pronucleus
at the time of the metamorphosis of the ‘“ Ammocetes” into the adult.
“‘ Aber diese Auffassung (Calberla’s) verliert allen Boden durch den von
uns gefiihrten Nachweis, dass am Beginne des Befruchtungsactes ein Rich-
tungskorper eliminirt wird” (p. 20). The proof is not entirely satisfac-
tory to me, for I do not see what direct evidence has been produced to
show that the supposed polar corpuscle may not have been eliminated
from the yolk at a much earlier period than that of fecundation. That
it might after elimination become enveloped by the yolk, — which be-
fore fecundation fills completely the egg membrane, — and thereby
* The signification of this “ Dotterhiigel”’ and its relation to the first plane of
segmentation will be discussed hereafter. See p. 499.
T See the account given elsewhere (p. 501) of the changes accompanying fertiliza-
tion.
460 BULLETIN OF THE
escape observation, cannot be considered strange, since similar changes
resulting in the obscuration of polar globules have been frequently ob-
served. Subsequent statements furnish the only ground presented for
such a conclusion. The authors found, namely, on eggs taken from fe-
males ready for oviposition, that there was constantly a large, flattened
lenticular nucleus near the active pole in the superficial layer of trans-
lucent protoplasm. This is comparable, they believe, with the germina-
tive vesicle of birds’ eggs, and with that which O. Hertwig has figured
for mature batrachian eggs ; it is, however, smaller than the latter, but
larger than, and not comparable with, the deeply situated nuclear struc-
ture (Kikern) shown by Calberla in his Figs. 3 and 4. This germinative
vesicle, from its position and size, just covers the dark spot called by
Calberla “inner micropyle.” After fertilization the place of the vesicle
is occupied by a clearer mass, but it is difficult to determine its limits
on hardened eggs.
Before the protoplasmic “ Zapfen” (“ Dottertropfen” of Calberla) dis-
appears, one observes that a globular, granular body arises within its
previously clear mass, and that it is ejected (second polar globule) from
the “ Zapfen” as the latter sinks again into the yolk.
In Clepsine the germinative vesicle gives place, according to WHITMAN
('78", pp. 13-49, Figs. 1-9, 60-67), to a bistellate figure, which is
called “archiamphiaster,’” while the egg is still in the ovary. The
details of the process were not observed. In the earliest stages seen
the axis of this archiamphiaster is inclined to that radius of the egg
which passes through the centre of the amphiaster, but later this obli-
quity disappears, and the axis of the figure coincides with the radius.
The most conspicuous parts are the two poles, encircled as they are
with well-defined radial lines which extend out into the densely packed
yolk spheres some distance beyond the polar “areas.” The central part
of the area is more deeply colored with carmine than its peripheral part.
Between the two poles is a more or less spindle-shaped space free from
yolk spheres. This corresponds very nearly with the germinative vesicle
in size. Within this space the radial lines of the two stars are con-
tinuous from pole to pole. These interstellate lines appear to differ in
no essential way from the other radial lines. In only two preparations
was anything found comparable to Strasburger’s Kernplatte, and in
these cases of so doubtful a character that they were omitted from the
drawings. Whitman is inclined from this to regard with favor Fol’s idea
that the spindle fibres are identical with the stellate rays, and only
appear different since they are surrounded by different media. The
|
|
|
MUSEUM OF COMPARATIVE ZOOLOGY. 461
archiamphiaster is already formed at the time of extrusion, and usually
has a radial position with one pole so near the surface that it gives rise
toa “polar figure” visible on the living egg as a white spot with dis-
tinct radial structure. After the archiamphiaster is formed, the egg,
provided it is not extruded and brought in contact with water, may
remain in a quiescent condition for at least two (or perhaps for even
four or five) days, without any injury or abnormal effect upon its:
development. There appears in the centre of the ‘ polar figure” about
half an hour after extrusion a minute pedlucid spot which is entirely free
from yolk spheres and granules. This is the central part of the polar
area of the outer star, and is deeply stained in carmine. I have else-
where (p. 421) alluded to the significance of this pellucid spot. Although
the subject is not formally discussed by the author, it seems to me that
he leaves the impression that he regards this polar corpuscle ‘‘C’. P.” as
the beginning of the new nucleus. At least, he says, a similar ‘“ pellucid
spot” is seen immediately after the formation of the second polar glob-
ule, and marks the place of its exit (p. 20). A section of the egg at this
time shows beneath the globules a circular space free from deutoplasm,
open toward the globules, and filled with a very fine granular substance,
which has the lead-gray tinge characteristic of the germinative vesicle
that has been treated with osmic acid. This body, which appears as a
pellucid spot on fresh eggs and which may be designated with Van Bene-
den and Fol as female pronucleus, says Whitman, is the remnant of
the archiamphiaster. Thus indirectly we may infer, I think, that the
first-mentioned ‘“‘pellucid spot” was estimated by him to be a nuclear
structure. As far as I can judge by comparison with other objects, I
am inclined to think that no part of the Kernplatte is embraced in these
pellucid spots. I am not so confident that no part of this areal corpus-
cle enters into the composition of the female pronucleus in the case of
Clepsine. To judge from what takes place in Limax, it is to be ex-
pected that this corpuscle in the polar cells, at least, takes no part
whatever in the nuclear structure. If it shall hereafter be possible at
any time to trace the fate of the Kernplatte, the question may be defi-
nitely settled ; till then I can only believe that there is no essential
variation in Clepsine from what I have seen in Limax.
The formation of the polar globules in C. marginata is accompanied
by a very interesting change in the form of the egg, first observed by
Whitman. About thirty minutes after extrusion a marked constriction
of the egg at the equator becomes visible ; this constriction without be-
coming very deep advances slowly and uniformly toward the pole where
462 BULLETIN OF THE
the pellucid spot is located. In from ten to fifteen minutes it is com-
pleted, leaving only a nipple-like protuberance from which the first polar
globule begins to emerge. “That part of the polar globule first to
appear is perfectly transparent, but the half last eliminated is filled with.
minute, highly refractive granules, the outer border of which forms a
straight line at first.” After its elimination, the yolk, which had re-
ceded from the vitelline membrane at the formative pole of the egg;
again fills out the perivitelline space coming in contact with the mem-
brane, and thus the polar globule is pushed so far back into the yolk
that it is seen with difficulty. A similar, but not so marked or regular,
peristaltic constriction accompanies the formation of the second polar
globule. In C. complanata the furrow often appears raised in the
middle, giving it the appearance of being double. It is possible that
the same phenomenon has been fixed by reagents in the Limax egg
shown in Fig. 55.
The fate of the germinative vesicle and the significance of the polar
globules are discussed by Whitman at some length. The germinative
vesicle is not totally eliminated, so there is really no enuclear or cytode
stage, which, moreover, from a priort grounds could hardly be expected.
“Ontogeny furnishes numerous examples of reversion, but I believe no
case in which reversion is followed by progression to the same point —
again.” Although the genetic connection of the archiamphiaster and
the germinative vesicle were not absolutely demonstrated in Clepsine,
yet, granting this,. “the proof in Clepsine is as complete as it well can be
for opaque eggs that a part of the germinative vesicle persists as a nu-
clear element ” (p. 34).
The occurrence of polar globules the author thinks still a matter of
doubt in birds, reptiles, amphibians, most fishes, tunicates, arthropods,
and rotifers. I have shown it to be highly probable, however, that Stras-
burger has seen stages initiatory to the formation of a polar globule in
Phallusia.
Whitman maintains that it is impossible to make a direct comparison
of the elimination of the entire germinative vesicle, as represented by
Balfour and Oellacher, with the formation of polar globules by amphias-
tral division. The “pole-cells” in insects, as they form the basis of the
sexual organs, cannot be equivalent to polar globules; nor can the so-
called “testa-cells” of the ascidian egg.
Perhaps the most interesting part of Whitman’s discussion is that
which considers the historic origin of the polar globules (pp. 44—49), to
which the reader must be referred, since there is space here for only 2
MUSEUM OF COMPARATIVE ZOOLOGY. 463
brief account. The objection to Biitschli’s theory, that the formation of
polar globules is equivalent to the elimination of the “ nucleolus,” which
occurs in many Infusoria as a result of (temporary ?) conjugation, is found
in the fact that the polar globules are formed independently of fecunda-
tion, while the “nucleolus” of Infusoria is ejected as a consequence of the
conjugation.
The view held by Biitschli, that the production of polar globules is a
process by which the nucleus is rejuvenated, —a phenomenon, not. of
the maturation of the egg, but of the earliest phase of its development,
which may take place either parthenogenetically, or under the influence
of fecundation, — and therefore that the meaning of this process is to be
sought in the elimination of a part of the egg nucleus, is not, according to
Whitman, the interpretation “most in harmony with the phenomena of
conjugation, the characteristic feature of which is the addition rather
than the removal of substance.” For this reason the forms both of total
and of temporary conjugation observed among Infusoria are fundamen-
tally the same, the latter being, so to speak, an abridgment of the former.
“Tmpregnation in both plants and animals consists,” says Whitman,
“in a complete and permanent fusion between corresponding parts of
two unicellular individuals, fully analogous to what happens in the first
mode of conjugation, with this difference, that polar globules and ‘canal
‘cells’ are produced before the fusion begins, or at least before it is com-
pleted,” but not so in the case of conjugation. “In what relation, then,
do polar globules stand to impregnation?” “That there is no necessary
_ [eausal] connection is in harmony with the absence of such corpuscles in
- conjugation.” A temporal relation, however, does exist. Whitman
adopts the view which homologizes the “canal cells” of plants with the
polar globules. In the former the “canal cells” stand at the end of a
series of asexual generations, the impregnated ege beginning a new series
that will end like the preceding. “Just as fecundation in plants is fol-
lowed by cell proliferation culminating in sexually differentiated cells,
: destined to copulate and renew the cycle of changes, — all other products
of the proliferation (canal cells with the rest) eventually dying out, — so
| in Infusoria conjugation is succeeded by reproduction by fission, the ulti-
| mate products of which are sexually differentiated individuals. The
| chief difference here is, that in one case (Infusoria) all (?), in the other
}
| only a comparatively few, individuals become capable of gamic repro-
;
duction ; but this difference, having reference only to a specialization of
,
| function which necessarily accompanies the development of a multicellu-
» lar organism, authorizes no fundamental distinction. In Metazoa, like-
464 BULLETIN OF THE
wise, a gamic cell-generation is followed by a line of agamic generations,
the last of which are the small cells called by Robin polar globules.
With the production of these globules we arrive at the sexually ripe egg,
In accordance with all this, I interpret the formation of polar globules as
a relic of the primitive mode of asexual reproduction, which normally pre-
cedes fecundation, and is therefore no part of the process of impregna-
tion. This interpretation accounts for the otherwise inexplicable fact
that amphiastral divisions of the nucleus introduce the formation of the
directive cells, and is in harmony with the absence of such cells in Infu-
soria, and their general occurrence among plants and animals.”
The subject of ‘polar rings” is considered in connection with that of
pronuclei, and both are reviewed farther on. (See p. 503.)
The second of the papers by O. Hertwic ('78*) of which a synopsis
was published in 1877 contains the results of studies. on ccelentrates,
worms, echinoderms, and mollusks. Among the celentrates the uni-
nucleolar is the prevailing but not the exclusive condition of the germi-
native vesicle. As in Asteracanthion the nucleolus is composed of two
substances of different refractive power. The eggs of Aiginopsis and
Mitrocoma when excluded are naked and agree with Toxopneustes in the
early formation and loss of the polar globules, which can be found only
by the study of eggs taken from the ovary. In Pelagia and Nausithoé
there are two or three polar globules, which are retained in contact
with the yolk by the gelatinous mass in which the eggs are laid, and
which contain one or several nucleolar structures. If three globules
are formed, the third arises by a division of the one first formed. All
the eggs which are ripe and excluded into the sea-water already possess
before fertilization a small homogeneous egg nucleus at the surface of
the yolk.
Of the Siphonophore the eggs of both Physophora hydrostatica and
Hippopodius gleba exhibited each two polar globules, mistaken by P. E.
Miiller in the case of the latter genus for spermatozoa.
Among the Ctenophore, Gegenbauria cordata exhibited constantly two —
polar globules, at some little distance from an egg nucleus which lay at
the boundary of the yolk granules and cortical layer of protoplasm. A
third body like the polar globules was occasionally seen a little distance
from the latter, but why he should suggest that it might be a sperma-
tozoon rather than a third polar globule, I do not understand.
The germinative vesicle of the immature eggs of Sagitta is peculiar in
having, instead of a single large nucleolus, a number of smaller nucleoli
which lie on the membrane of the vesicle. Also a reticular substance is
MUSEUM OF COMPARATIVE ZOOLOGY. 465
visible in the interior of the vesicle. The latter at maturity approaches
the surface of the yolk and is dissolved before the egg leaves the ovarium.
In eggs treated with acetic acid the Richtungsspindel was observed to
have a peculiar structure. It was composed of a bundle of stout, short,
lustrous rods of -uniform thickness throughout, and so arranged as to
appear in optical cross-section as a circle of conspicuous granules. The
formation of two polar globules, and the subsequent appearance of an
“eoo nucleus ” ‘(at first as a small vacuole in the periphery of the yolk
under the polar globules), were observed in the living egg to follow each
other after intervals of a quarter of an hour only. In already excluded
egos of Alciope a maturation spindle of considerable size was observed.
The germinative dot in eggs of Ascidia intestinalis, as well as in Physo-
phora, in Spheerechinus, and in several mollusks (Unio, Tellina, Helix),
was found to be really composed of two substances, having, as in the
case of Asteracanthion, different physical and micro-chemical properties.
To designate these Hertwig uses the name Juwclein, for the larger, less
refringent, and usually enveloping substance ; and Paranuclein, for the
smaller body. As the names imply, he considers the former as the
essential part and the latter as the accessory part. This he does not-
withstanding the fact, already established by his studies on Asteracan-
thion, that the “ Paranuclein” (as I conclude from the account of its
deportment in the two cases) is the part which is “7m erster Linie”
engaged in the transmigratory changes accompanying the formation of
the first maturation spindle. Flemming, moreover, holds, as Hertwig
states, the reverse opinion as far as regards the case of lamellibranchs.
Hertwig gives figures from his earlier studies on Heemopis which now
have greater interest in view of his observations on the starfish. They
represent stages in the formation of the ‘“ Richtungsspindel” when por-
tions of the nuclear substance are still to be found in the vicinity of the
spindle figure. These bodies entirely disappear with the completion of
the spindle, i. e. by the time the polar globules begin to be formed.
The formation of two polar globules in the sea-urchin (Spherechinus
brevispinosus) takes place in nearly the same manner as in the star-
fish, except that the two maturation spindles and archiamphiasters are
larger. Hertwig acknowledges that his previous representations of the
metamorphosis of the germinative vesicle were produced from eggs in
a pathological condition. The reason why the maturation spindle was
not previously found in mature eggs is explained by the polar globules
being formed in the ovary, and at a time when the eggs do not pos-
Sess a firm membrane, so that the latter are lost in the ovarial fluid.
"OL. VI.—NO. 12. 30
466 BULLETIN OF THE
The eggs of the sea-urchin are peculiar from the great length of time
(sixteen to eighteen hours) during which they remain capable of normal
fertilization. The abnormal penetration of several spermatozoa Hertwig
thinks is due to the protoplasm, impaired in its vital energies, no longer
offering resistance to such penetration. .
Among mollusks the eggs of Mytilus afforded excellent results, which
in the main so far corroborate the evidence of his other observations
that I confine myself to a few minor points. Before the first maturation
spindle has reached the surface of the yolk a corpuscle (sometimes
divided into halves) is seen at some distance from the spindle. He is
not quite certain, but inclines to the opinion that it consists of nuclear
substance, for it disappears some time after fertilization, i.e. before the
formation of the polar globules. It is interesting to observe that the
ege does not advance beyond the formation of the first maturation spindle
unless it is fertilized. Then, after fifteen minutes, the polar globules are
quickly formed (the second follows the first after twenty-five minutes),
and carry before them the double-contoured egg membrane. The spindle
becomes shortened and thicker before the globule is formed. A promi-
nence arises at the vegetative pole of the egg when the first cleavage
amphiaster makes its appearance; it ultimately forms a part of the
greater (vegetative) segmentation sphere.
The criticism I have made on the account given by Fol of the early
changes in pteropod eggs, simply from a comparison with the changes
which occur in Limax, is strengthened by the conclusions to which
Hertwig arrives from a study of mollusks more nearly related to those
investigated by Fol. It follows from Hertwig’s -observations on Tiede-
mannia Neapolitana and Cymbulia Peronii that the formation of polar
globules and of the egg nucleus takes place in essentially the same
manner as in Asteracanthion. The two polar globules are formed one
after the other, — not by the division of a single globule. The “ Ver-
dichtungszone” of the maturation spindle may in Tiedemannia be seen
in the living egg as a row of short dark rods.
He passes over the formation of the second maturation spindle by
simply saying that the spindle-half which remains after the second polar
globule is formed, completes itself again. The female pronucleus arises
as a cluster of vacuoles. It is noticeable that in all the mollusks de-
scribed by Hertwig, except lamellibranchs, it remains very near the
animal pole of the egg just as in Limax, and that in all cases the
female pronucleus, unlike Limax, seems to exercise less influence on
the surrounding protoplasm than does the male pronncleus.
a ieee o :
MUSEUM OF COMPARATIVE ZOOLOGY. 467
The phenomena in Pterotrachea and Phyllirhoé are so nearly the same
that they are described jointly, and afford excellent results on the nature
of the metamorphosis. The spindle is formed within, and therefore out
of the substance of, the germinative vesicle. On preparations made with
acetic acid the spindle is found to lie through the middle of the vesicle
(or a little eccentric), its ends with their extensive asters lying at two
poles of the vesicle where its wall has been dissolved. The coagulated
nuclear fluid (Kernsaft) is distinguishable after the membrane of the
vesicle has been entirely dissolved. When the spindle has taken a radial
position the yolk exhibits a depression at the point where one of its ends
reaches the surface. The second spindle is much smaller than the first.
While I can fully acquiesce in a majority of the points defended by
Buancuarp (78, pp. 747-754), I cannot think all the conclusions he has
reached are justified by the literature which he has so recently reviewed.
It is at least confusing for him to say, “The germinative vesicle disap-
pears, not because it is dissolved in, but because it is expelled from the
vitellus, just as Pouchet maintained thirty years ago,” even though he
subsequently gives a less prejudiced account of these changes. It is
likewise very unsatisfactory, because incomplete, to say that the germi-
native vesicle in escaping from the vitellus leaves behind in the yolk
a part of its fluid (suc) in a state of solution. That I may not mis-
represent the conclusions of Blanchard, I must add that he recognizes
the derivation of the female pronucleus from the half of the second
spindle which remains in the vitellus and “ se désorganise.” I do not
understand how a process of disorganization can result directly in the
construction of a new nucleus, and cannot share the belief that the
spindle metamorphosis of the germinative vesicle is “a consequence of
its natural death,” since thereby I should be compelled to look upon
the spindle metamorphosis which accompanies every subsequent cell
division — although presenting the most striking evidence of activity —
as a consequence of the death of the nucleus! One should not maintain,
as Blanchard does, that the polar globules exercise a considerable influ-
ence on the direction of the segmentation furrows and the reciprocal
relations of the blastomeres. It cannot be doubted that there exists a
constant spatial relation between the polar globules and the furrows,
but to seek the cause of this coincidence in a supposed influence of the
polar globules over the position of the furrows is to adopt an explana-
tion of which there has as yet been adduced no proof, and which is much
less satisfactory than that which makes the position of the place both
where the polar globules shall emerge and where segmentation shall
468 BULLETIN OF THE
subsequently begin depend upon the same cause (not yet fully under-
stood), a cause which effects the segregation of the more active con-
stituents of the egg about the pole in question before ether of these
phenomena have taken formal expression.
Blanchard pertinently objects to Rabl’s theory of the protective office
of the polar globules, on the ground that, if injurious pressure were
exerted by the egg membrane, the globules would only serve to increase
its damaging effect by concentrating the pressure upon a more limited
extent of the embryo’s surface, and thereby necessarily increasing pro-
portionally the intensity of the pressure.
3. Fecundation.
It is my purpose to review such papers as treat the subject of fecun-
dation in the light of the recent discoveries of nuclear copulation, or such
as have paved the way to so fundamentally important a conception of
the nature of the process in question. The order in which these phe-
nomena have been discovered has been nearly the reverse of the succes-_
sion in which the events of fecundation make their appearance. It was
in the earlier part of the present decade that a beginning was made in
divesting the /ater stages of fecundation of some of their mysteries, and
only by a sort of retrogressive exploration that we have within the past
two or three years come to understand better the earlier stages of the
process, and to put all in more satisfactory correlation.
~ Burscuur (737) was one of the earliest observers to trace some of the
changes which overtake the pronuclei, but he could give no account of
their origin, and therefore had no idea that they were intimately con-
nected with the fecundation of the egg, as he also was in doubt about
their actual coalescence. His account of the phenomena accompanying
their union has been, for the sake of convenience, given in another
connection (pp. 280, 396).
The studies of Wert (73) I am only acquainted with through Hof-
mann and Schwalbe’s ‘‘Jahresbericht,” etc., from which it is to be learned
that he has observed in rabbit eggs taken from the oviduct between
seventeen and forty-six hours after fecundation (should probably read
“after copulation ”) living spermatozoa, in four cases within the egg
protoplasm itself. Like Van Beneden, Weil also saw two nuclei (male
and female pronuclei) before the beginning of segmentation.
What has already been said of the origin of the female pronucleus, as
described by Auerbach, is true of the male pronucleus. Concerning the
further changes of the pronuclei after they meet in the centre of the
MUSEUM OF COMPARATIVE ZOOLOGY. 469
egg, AumRBacH (’74, pp. 210-217) says that they continue their mo-
tion until they become, to a considerable extent, mutually flattened.
The line of contact is very fine, and the failure of the nuclei to melt
together at once is due to that condition of the surface of the two nu-
clear drops known to physicists as superficial tension, and not to the
existence of a veritable nuclear membrane. ‘The flattened pair of nuclei
soon commence a rotary motion around an axis perpendicular to the
long axis of the egg, which continues till the plane of separation, which
originally was perpendicular to the long axis, comes to lie parallel with
it. The rotation, like the migration of the nuclei, is passive, i. e. is
effected by the contractility of the protoplasm. Toward the end of this
rotary motion the nuclei become more flattened, and the nucleoli be-
come, one after the other, gradually paler and somewhat larger, and
then suddenly their substance scatters, forming a cloud, which almost
immediately vanishes. After this the line of separation suddenly dis-
appears along its whole extent, and the two nuclei are one. If it were
a layer of protoplasm or a membrane which separated the nuclei, it
could not disappear throughout its entire length at the same instant.
The single nucleus by elongation now assumes a rhombic or broad-
spindle form.
When he comes to an interpretation of the meaning of this melting
together of two nuclear structures, Auerbach believes that it is to be un-
derstood as a sort of conjugation (pp. 248, 249), — a necessary introduc-
tion to the process of successive nuclear increase, which is soon to follow.
Hence it is a kind of nuclear reproduction. Just as for the reproduction
of individual organisms a copulation of two individuals is so often indis-
pensable, so for unicellular organisms is that of two cells. Every conju-
gation has manifestly for its end the improvement (by a process of
intermingling) of individual peculiarities, —the mutual complementing
of deficiencies. A difference in the two uniting elements, so common
elsewhere, is not wanting here. ‘The difference in the place of origin of
the polar nuclei —the one at the smaller pole where the spermatozoa
penetrated, the other at the opposite pole — will influence the quality
of the nuclear material and induce one-sided faults in the composition of
each. To correct this is the object of the migration and confluence of
the primitive nuclei. But if these were simply to meet and coalesce,
then, owing to the inability of the thick nuclear fluids immediately to
intermingle, the whole process would be futile, since with the first
segmentation each half of the nuclear mass would be relegated to the
half of the yolk in which it arose. This is obviated by the rotation of
470 BULLETIN OF THE
the mass through 90°, whereby each half supplements the half of its
own nuclear fluid by the half of that which arose at the opposite pole of
the egg.
In Cephalobus rigidus Butscuut ("75, p. 202) says he has seen the
process of fecundation in the most satisfactory manner. As soon as the
egg reaches the first spermatozodn of the seminal vesicle it unites with
it at once. The spermatozoon attaches itself closely to the surface of
the yolk, and when the latter has entered the uterus appears already
fused with it. The egg certainly combines with no other spermatozodn
in its passage through the seminal vesicle. In Cucullanus the egg at
the moment of fecundation was not observed, but fecundated eggs dis-
closed clearly the entered spermatozoén as a cluster of dark granules sur-
rounded by a clear area. It is therefore not at once fused with the yolk
in this case. The results reached in this preliminary account regarding
the origin and fate of the pronuclei I have given in connection with the
subject of maturation (p. 403). Biitschli fails to connect either of the
pronuclei directly with the penetration of a spermatozodn, but attrib-_
utes the beginning of the maturation phenomena to the influence of
fecundation. Since by the ejection of the polar globule a component
of the nucleus is removed, it is readily to be inferred that the same is
replaced by components of the spermatozodn, especially since subse-
quently (during segmentation) a part (spindle) corresponding to the
polar globules is found in the nucleus. There is ground for the state-
ment that the essential thing in fecundation consists in the removal of
the old nucleolus, and the formation of a new one to which elements of
the spermatozodn contribute (p. 210). .
For Bombinator GorttEe (75, pp. 51 et seg.) describes the disappear-
ance of the germinative vesicle, which leaves behind for some time a
starlike figure in the upper half of the yolk. Immediately after fecun-
dation in the more advanced eggs, a “yolk nucleus ” (Dotterkern) has
already made its appearance near the middle of the egg as a large,
round, somewhat flattened body, with distinct but not sharp contour.
The finely granular substance of the disintegrated germinative vesicle
reaches within its territory, but with such want of uniformity as to
justify the assumption that the two structures sustain only a chance
relationship. This “Dotterkern” migrates toward the upper pole of
the egg, while the discoloration of the yolk, due to the disintegration of
the germinative vesicle, disappears entirely ; and thereupon is formed
within it a delicate round corpuscle —the first “ Lebenskeim ” — which
induces the further development of the egg. This “life germ” per-
MUSEUM OF COMPARATIVE ZOOLOGY. A71
sists when, soon after, the yolk nucleus becomes faintly outlined and
disappears. .
As I have elsewhere indicated, it is probable that Fou (75%, Pl. VII.
Fig. 2, and Pl. VIII. Fig. 2) saw and figured for Pteropoda, without com-
prehending its true significance, the male pronucleus, both some time be-
fore and also when it was about to join the female pronucleus, in the
former case as the centre of a well-expressed aster.
O. Hertwie (75, pp. 378-398, Taf. XI.) was the first to definitely
connect one of the pronuclei (Spermakern) with a spermatozoon. In
from five to ten minutes after artificial fertilization of the eggs of the
sea-urchin there appears near the surface a small clear space from which
the yolk granules have disappeared. This space increases a little in size,
and at the same time the neighboring yolk granules assume a radial
arrangement about it as a centre; at first limited to its immediate
vicinity, but gradually becoming more extensive and more distinct. A
small homogeneous body makes its appearance in this space, from which
it only slightly differs in its refractive power. Sometimes a delicate line
was seen stretching from this body to the periphery of the yolk, whence
it continued into the perivitelline space as a fine thread. This radial
figure migrates rapidly (requiring only about five minutes) from the
periphery to near the centre of the egg; here the corpuscle encounters
the “egg nucleus” (female pronucleus), which has meantime slowly
approached the stellate figure. The egg nucleus has a diameter of 13;
the corpuscle, of 44. The nucleus now undergoes a slight ameboid
change of form, both structures become less distinct, and the smaller
finally disappears. A little later the limitation of the egg nucleus again
becomes distinct, but the smaller body is not to be seen. The nucleus
is larger than before, and of spherical form. Meanwhile the stellate
figure, in which the egg nucleus has now come to lie, has increased in
extent till its rays reach nearly to the periphery of the yolk on all
sides.
The use of osmic acid and Beale’s carmine confirms the results of these
observations on living eggs. The stellate figure is, however, less conspic-
uous than in the fresh condition. By this treatment it is found that
both the egg nucleus and the central corpuscle of the stellate figure be-
come deeply stained. This warrants the conclusion that both consist of
nuclear substance. The corpuscle is a little more intensely colored than
the egg nucleus, a condition to be accounted for by the more compact
condition of its substance. Furthermore, stages in which the two nuclear
structures are in contact, and later such as show only a single nuclear
472 BULLETIN OF THE
structure, justify the opinion that the single nucleus found in the egg
emmediately before segmentation, and surrounded by rays of yolk granules,
as the result of the copulation of two nuclei. Hertwig also reports that,
while in most cases only one clear spot makes its appearance in the pe-
riphery of the yolk, occasionally more (up to four) have been observed to
make their way to the egg nucleus ; but after the appearance of anoma-
lous nuclear figures, the eggs soon perished. It is therefore probable
that these eggs were from the beginning pathologically altered.
In the interpretation of these observations he concludes that the con-
stancy of their appearance at a uniform interval after the mingling of the
sexual elements is evidence that they are dependent on fertilization.
From this and the observed filament it is not to be doubted that these
changes are referable to the penetration into the yolk of a sperma-
tozoon, of which the tail is the observed filament, while the head (its
nucleus) becomes the ‘‘Spermakern.” The tail is probably dissolved
either at once or during the migration of the sperm nucleus. The
homogeneous protoplasmic area and the radial figure are apparently
induced by the sperm nucleus which occupies their centre, in the fol-
lowing way: the nucleus exerts an attractive influence on the homoge-
neous components of the yolk, which thus become most densely collected
around the nucleus, and thence radiate in all directions. The yolk gran-
ules passively assume a position in the interstices between the rays of
the attracted substance.
The most important part of fecundation, hitherto explained as the
copulation of two cells,* is found in the fusion of the two nuclei from
which “arises first a nucleus (nucleus of the first cleavage-sphere)
equipped with living forces, which effectively stimulates, and in many
respects controls, the further process of development in the yolk.”
In a foot-note (p. 386) Hertwig calls attention to the fact that for the
time being the egg cell may be considered as in an hermaphroditie condi-
tion, inasmuch as two sexually different nuclei are present in a common
protoplasmic mass. Further, since the “nucleus” and the “nucleolus ”
of Infusoria are, from the changes they undergo in reproduction, com-
parable with the egg nucleus and sperm nucleus respectively, it follows
that the Infusoria may be considered as hermaphroditie unicellular organ-
isms, inasmuch as the sexual differentiation of the nuclear substance,
which has been accomplished in other organisms in two separate cells, is
with them effected in a single cell.
In a foot-note Burscati (75%, p. 109) says his recent studies tend to
* See Haeckel "74, pp. 135-138, and "75, pp. 482, 483.
MUSEUM OF COMPARATIVE ZOOLOGY. 473
confirm his opinion that the essence of fecundation consists in a total or
* partial renewal of the nucleus of the egg cell.
Hensen (75, p. 238, Taf. VIII. Figs. 5-8) never saw ‘ein Samen-
fidchen in den Dotter hinein kriechen,” but has often seen these cor-
puscles imbedded, either entirely or the head only, in the yolk in the case
of the guinea-pig and the rabbit, and draws the general conclusion
(p. 241) that in the case of these animals more than one spermatozoon
can penetrate the yolk, where, under definite formal changes of the
head, it is dissolved, and that in this manner the fecundation of the egg
is accomplished.
Ep. vaN Benepen (75, pp. 693-695) was never able to observe the
penetration of a spermatozoon into the vitellus of the rabbit’s egg ; but
from often finding spermatozoa very closely adherent to the surface of
the yolk, he ventures to express the belief that ‘“ fecundation consists
essentially in the fusion of the spermatic substance with the superficial
layer of the vitelline globe.” His account of the formation and union of
the pronuclei is given on pages 412 to 414.
The penetration of spermatozoa into the egg, which Rosin maintains
(75, p. 21), does not imply a penetration into the yolk substance. The
ultimate molecular union of the substance of a large number of those
which penetrate the membrane and are liquefied, is evidently only an
inference from a supposed diminution of those still found in the peri-
vitelline fluid at later stages (see Robin ’62, p. 87). ‘The retraction of
the yolk, the changes which supervene in its granules, the formation
of polar globules, are partial phenomena which occur with eggs whether
fecundated or not ; but the production of the witelline nucleus only takes
place in ovules into which spermatozoa have penetrated, i. e. [in ovules]
to the vitellus of which male substance has been united.” (75, p. 86.)
Notwithstanding the accuracy of the greater part of this statement, it
does not follow that the author understood the true origin of the nucleus
of the first segmentation sphere,— his ‘“‘noyau vitellin.” In fact, it has
in his opinion an origin entirely independent of the germinative vesicle,
at the centre of the yolk, by a molecular association of “ principes immé-
diats” of the vitellus. It is with the appearance of this nucleus that
the ovule takes on the characters of a new being, and ceases to be an
anatomical element of the adult animal which produces it.
Thus, of all the parts which compose the ovule before maturity, the
vitellus, he believes, is the only one which serves for the production of a
new being.
I shall not reproduce the second part of Van Benepen’s (’76%, pp. 76 -
474. BULLETIN OF THE
83, and ’76°, pp. 178-182) paper * on the germinal vesicle and the first
embryonic nucleus, for it is an attempt to harmonize Hertwig’s observa-
tions on Toxopneustes with the author’s own studies on mammals, which
was only made possible, as Hertwig (77, p. 77) himself has very clearly
shown, by a misconception of the account given by the latter. Van
Beneden’s assumption that Hertwig’s ‘“‘Spermakern” is a nucleolus finds
no support in Hertwig’s description, and the protoplasmic area surround-
ing it is certainly not a nucleus, and therefore not comparable with Van
Beneden’s “pronucleus périphérique.” While there is no reason to
question the interpretation which Van Beneden assigns to his own ob-
servations, his attempts to subject Hertwig’s observations to an unnatu-
ral alliance with his own must be regarded as unsuccessful.
In the egg of the common toad after fertilization Van BamBexe (76,
pp. 117-135, Pl. II.) has observed that meridional sections exhibit, in-
stead of a single pigmented trail, —the claviform body of the unfertil-
ized ege, —two such trails. One of these, the “trainée en boudin,” is
slightly swollen at its internal end, and reaches nearer to the centre of
the yolk than the second, — “trainée triangulaire,” — about the inner
end of which it is curved as about a centre. At its periphery it abuts
upon the germinative fossa. This the author thinks is unquestionably
the claviform figure of the unfertilized egg made to take a curved course
by the pushing in against it of the second or triangular trail. The latter
is also mingled at its base with the pigmented cortical layer of the supe-
rior half of the egg; its apex is directed inward, and is slightly curved
upward so as to terminate in the space surrounded by the curved “ trainée
en boudin.” In the terminal part of the triangular trail was once seen
a clear homogeneous point limited by a strongly pigmented contour,
which the author considers the nucleus of the first segmentation sphere.
Similar conditions are found in fertilized eggs of Pelobates. Here,
however, the claviform figure is not curved, and its inferior enlargement,
in place of being a pigmented mass, is less deeply colored than the zone
which immediately surrounds it. The apex of the triangular trail, hay-
ing come to occupy the centre of this enlargement, is seen to abut upon
an elliptical nuclear mass (nucleus of first segmentation sphere), which
is a little clearer than the surrounding yolk, and is limited by a pig-
mented contour, whence granular striations of the yolk radiate.
Observations of a similar kind on the eggs of the Axolotl convince the
* The English translation of this paper ("76°) exhibits an omission which is of
rather vital importance to Van Beneden’s argument. It may be corrected by insert-
ing, in the 15th line from the top of p. 181, “‘ nuclei of the” before ‘ cleavage spheres. ”
|
|
|
)
|
MUSEUM OF COMPARATIVE ZOOLOGY. 475
author that the triangular trail of the tailless Batrachia is homologous
with that which takes its origin from the “ trous vitellins,” as previously
described by him (’70, pp. 64, 65). Finally, after a review of the liter-
ature, Van Bambeke arrives at the conclusion that the eggs of the
Batrachia, immediately after impregnation, still embrace traces of the
claviform figure, but nothing discloses the presence of the ‘“ EKikern” of
Hertwig, or the “ pronucleus central” of Van Beneden. The nucleus of
the first segmentation sphere arises from the periphery ; it very probably
results from the penetration into the vitellus of a spermatozoon, which
leaves as a trace of its passage the “trou vitellins” and the “trainée
pigmentaire.”
In Nephelis, after the conversion of the germinative vesicle into a
nuclear spindle, Burscuti (76, pp. 216, 217) has seen a little elevation
of clear protoplasm near the animal pole of the yolk, and believes it is
caused by the union of a spermatozoon. with the yolk, during which the
spermatozoon, possibly by swelling, has become metamorphosed into the
protuberance.
Other phenomena, which Biitschli did not think of connecting with
fecundation, are probably phases of that process. The “third” system
of rays about a homogeneous area we may now safely infer to be the
male aster. The relation which the nucleus (male pronucleus) sustains
to this ‘‘area” deserves attention. According to the text, “it always lies
nearly in the periphery of the central area.” From Fig. 3, Taf. L, it is
evident that it lies in that part of the periphery nearest the female pro-
nucleus. I do not know of any other observation which agrees with
this in the particular last mentioned. In eggs of Cucullanus that
have passed the seminal receptacle (p. 223), a clear corpuscle, which en-
closes a cluster of granules, is found imbedded in the surface of the yolk.
‘ It is, says the author, the result of the union of a spermatozoén with the
yolk (see Taf. III. Figs. 1, 7, 12). It, however, disappears before the
beginning of the formation of new nuclei. The latter arise close under
the surface of the yolk, and are from the beginning distinctly vesicular,
with dark envelope and granular contents, but never acquire a special
nucleolus. They migrate toward the centre and become fused into a
single nucleus. In Anguillula rigida (pp. 232, 233) the egg unites with
the first spermatozodn with which it comes in contact, but never with a
second.
In the mollusks studied (p. 238) the first evidence of the existence of
a male aster was observed (Lymnzus) when the first polar. globule had
been eliminated. It already occupied the centre of the yolk. A nucleus
476 BULLETIN OF THE
(male pronucleus) was not observed in connection with this aster. From
among the large number of nuclear structures (nine in Lymnzeus) that ap- —
pear in the yolk under the place of the polar globules in Biitschli’s figures,
it is not possible to say always which represents the male pronucleus,
though there is usually one (Taf. IV. Figs. 7-9) which from its deeper
position or larger size may perhaps be inferred to be such.
In Succinea the pronuclei closely resemble those which I have found
in Limax, the membrane (?) being much wrinkled by the action of acetic
acid. In Fig. 23 of Biitschli’s Taf. IV. the nuclei occupy a peculiar po-
sition, their plane of contact lying in the animal radius of the yolk. I
have never seen just such a relation. Whether in Succinea the male
pronucleus is at any time surrounded with a radiate structure of the
yolk, does not appear from Biitschli’s studies. I am inclined to think it
may be wanting, as in Limax. In view of the possible absence of stellate
figures in these cases, it still remains with me, as it was with Biitschli,
an open question, whether the central stellate figure of his Fig. 4 is
really a newly formed aster. Against the probability of its having any-
thing to do with the male pronucleus, it may be urged, in addition to
the probable absence of a male aster, that no nuclear (vacuolar) structure
was observed in its immediate vicinity, and that the aster occupies the
centre of the yolk at so early a stage. Biitschli evidently inclines to the
opinion that it has no genetic connection with the first spindle. If he |
is right, then it must be regarded as the male aster; but I am inclined
to believe, for the reasons just given, that it is the deeper star of the
second archiamphiaster, whose spindle has not been distinguished.
Biitschli endeavors (p. 391) to connect the “ Neubildung” of nuclei
in the first segmentation sphere with the segregation of very clear nearly
homogeneous protoplasm. It is usually collected at the place where the
polar globules emerge, but it may be more widely distributed over the
surface, and may even (Nephelis) collect at a point within the yolk.
This clear protoplasm forms the centre of a system of rays, and within it
the new nuclei arise from very minute beginnings. These beginnings are
small compact corpuscles (p. 408) which rapidly become differentiated
into small vesicles. Just as in the formation of the nuclei in cell divis-
ion, so here the simplest primitive form is farthest from Auerbach’s con-
ception, —an excavation in the protoplasm filled with a fluid, —it isa
homogeneous, compact condition. Since each of the several nuclei pos-
sesses the same histological structure as the nucleus which results from
their fusion, there is no ground for uniting with Selenka in calling the
former “nuclear germs,” nor for saying, with Strasburger, that they are
MUSEUM OF COMPARATIVE ZOOLOGY. 477
not so many individual nuclei, but that they furnish the material for the
construction of a nucleus.
A comparison with the conjugation of Infusoria leads Biitschli to the
conviction that in the fecundation of the egg similar modifications —
“total or partial renewal of the nucleus, or a material revival of the
same by the importation of a new part” — may be encountered (p. 438).
The two nuclei (pronuclei) are alike, and arise in the same manner.
There is ndt the least justification for interpreting them as egg nucleus
and sperm nucleus in O. Hertwig’s sense. The existence of a multiple
of nuclei is a phenomenon induced by the antecedent subdivision of the
nucleus of a spermatozodn which penetrated the yolk, not by the pene-
tration of several spermatozoa, as O. Hertwig concludes.
To ascertain whether the formation of polar globules is dependent on
fecundation the author instituted experiments on two nematodes (Rhab-
ditis teres and R. pellio) rearing <solated females. The eggs never
produced polar globules, and no changes of any sort overtook the germi-
native vesicle or dot until the yolk began to show signs of degeneration.
Biitschli concludes (p. 442) that both views are warranted, — that in one
case it is in consequence of, and in another independent of, fecundation,
but it is not a phenomenon of the maturation of the egg ; it is one of the
first of the phenomena of development, which in certain cases may take
place parthenogenetically before fecundation.
STRASBURGER (76, pp. 21, 295, Taf. II. Figs. 19-23, Taf. VII. Figs.
9-11) has given the following account of fecundation in Picea vulgaris
after the formation of a canal cell which remains in close contact with
the ovum. The pollen tube, making its way through the disorganized
cells of the neck of the archegonium, destroys the canal cell and reaches
_ the ovum, where its previously dissolved contents pass by a diosmotic pro-
cess through its very porous tip into the interior of the ovum, and are
taken up by the nucleus of the latter. This may take place in a con-
tinuous manner, or the contents may first be accumulated in a nucleus-
like structure at [i. e. outside] the end of the pollen tube, and then
advance to the “ EHikern,” or finally several such nuclear structures may
arise at the pollen tube and be successively received by the Hikern.
The latter, thus fecundated, Strasburger calls the germ nucleus, Keim-
kern ; it soon begins to disappear by a radial distribution of its mass in
the plasm of the egg.
His studies (p. 306) on the fecundation of animal eggs were made
upon Phallusia mammillata. In the first edition of this book Stras-
burger held that the “Keimkern” (segmentation nucleus) took its
478 BULLETIN OF THE
origin from the cortical layer (Hautschicht) of the yolk. This he now
corrects, and says the error was due to the “ Kikern ” lying in this case
(Phallusia) so near to the surface.* After new observations he accepts
the views of Hertwig in holding that the “‘ segmentation nucleus” arises
from the fusion of two nuclear structures. The sperm nucleus, which is
smaller than the egg nucleus, makes its appearance, according to Stras-
burger, in 14 or 2 hours after artificial fertilization, close to the outside
of the ‘‘ Kikern” between the latter and the Hautschicht, op. cit., Taf.
VIII. Fig. 4. It is at once surrounded with homogeneous protoplasm,
which is continuous on its peripheral side with the “‘ Hautschicht,” and
causes here a slight elevation of the surface. Rays emerge from this
homogeneous protoplasm, but around the egg nucleus there are none.
In another hardened egg (Taf. VIII. Fig. 5) he finds a larger single riu-
clear structure surrounded with rays, and concludes that it results from
the fusion of the germ- with the egg-nucleus. He does not, however,
agree with Hertwig, that the egg nucleus is the germinal dot, and from
a review of the studies of others on animal eggs concludes “ dass es sich
auch in den Fallen der Erhaltung des Eikernes nicht um diesen Kern
als morphologisches Element, sondern nur um dessen Substanz handle ”
(pp. 311, 312). An entirely parallel view is held touching the method
of the formation of the sperm nucleus. In the case of Phallusia it is
quite possible that the substance of the spermatozoa “ diffundirt ”
through the egg membrane, and re-collects within the yolk to form a
sperm-nucleus. In fecundation, then, it is probably a question of the.
introduction of nuclear substance into the egg, yet only as a physvological
element, not of the introduction of the nucleus of a spermatazoon as a
morphological element. .
“With the greatest care to prevent fertilization,” Grumrr (76%) has
raised the larvee of Asteracanthion rubens. The only difference between
the development of fecundated and unfecundated eggs consists in the
tardiness with which segmentation takes place in the latter case, — it
being ten to twelve hours after exclusion, instead of one to two hours, as
in fecundated eggs.
In his account of the development of Heteropoda, Fou (’76, pp. 113,
144) says that what remains of the star after the emergence of the polar
globule again approaches the centre of the vitellus and becomes rounded
into the form of a nucleus ; near the opposite or nutritive pole a second
nucleus appears, which also moves toward the centre. These nuclei em-
* T have elsewhere (pp. 420, 421) shown how probable it is that Strasburger has
in some cases confused another structure with the ‘‘ Eikern.”
MUSEUM OF COMPARATIVE ZOOLOGY. 479
brace nucleoli which become visible by the use of reagents. The nuclei
fuse and thus give rise to the ‘“nucléus secondaire, c’est-a-dire au nucléus
du vitellus fécondé et débarrasse des matiéres de rebut.” The source of
the second nucleus remained unknown to Fol, as clearly follows from
what is said at p. 144 :. “ From all these references, added to the results
of my own observations, it appears to follow that the vitellus possesses
after fecundation a central nucleus the origin of which is unknown.”
I have not had access to the original paper by Giarp (’76), but accord-
ing to R. Hertwig’s abstract Giard (’76’) defines fecundation to be a
copulation of the amceba (or amcebe) which is formed by the penetra-
tion of spermatozoa into the egg, with the egg amoeba which at this
moment relinquishes its encysted condition (disappearance of the germi-
native vesicle).
In a rabbit killed twelve hours after coitus, but not studied till ten
hours later, — the sexual organs having been maintained at a tempera-
ture not above 19° C.,—Campana (’77) found some spermatozoa fixed in
the superficial layer of the vitellus, and two still actively swimming
about in the perivitelline fluid. (!)
Fou ('77) confirms O. Hertwig’s observations of the penetration of a
spermatozodn into the vitellus ; the body of the spermatozoon appears
to fuse with the vitelline protoplasm to form a clear spot, which becomes
the centre of a system of radial striz. This Fol calls the male pronucleus.
He also reports similar discoveries for other animals. In Sagitta and
various Gasteropoda there is formed at the moment when the polar glob-
ules appear, and at the opposite pole of the yolk, a clear spot, surrounded,
in the case of Sagitta, with a star of protoplasmic filaments. This spot
moves toward the female pronucleus. During this motion one sees
very distinctly that the centre of the star is in advance of the clear spot,
and that the latter is drawn along in a passive manner. The female
pronucleus remains stationary till the clear spot is near at hand; it is
then attracted toward it, and the latter at the same time moves more
rapidly. The female pronucleus and the clear spot fuse to form the
nucleus of the fecundated egg. The direct evidence is wanting, but to
judge by analogy the clear spot is a male pronucleus.
This communication is particularly important, since it directs attention
to the relation of a pronucleus to its aster. I can to a certain extent
confirm this observation for Limax (see Fig. 68). It is of further interest
because it presents so just an estimate of the composition of the polar
globules. Still, the idea of their formation by a process of cell division
can hardly be said to have been fully grasped, to say nothing of the
480 BULLETIN OF THE
absence of such convincing proof of their nature as that soon brought
forward by another observer.
The fecundation of Asterias glacialis, as described by Fou (77%, p. 359),
is of great interest. The spermatozoa come in contact with the egg and
remain with the “body” imbedded in the mucous envelope which sur-
rounds the yolk. When one of them has succeeded in traversing half
the thickness of this envelope the protoplasm of the yolk accumulates
at the nearest point of its surface as a thin hyaline layer, which soon
rises in the centre in the form of a boss. This next changes to the
shape of a cone, and soon a fine thread of protoplasm establishes a
connection between the summit of the cone and the body of the sperma-
tozoon. The latter elongates, and, as it were, glides into the yolk, the
cue alone remaining outside, where it can be distinguished for some
time. Meanwhile the superficial hyaline layer increases in extent and
finally envelops the whole yolk. At the moment the connection with
the spermatozoon is established, this layer becomes clearly differentiated
and begins to detach itself from the vitellus as a vitelline membrane.
This differentiation commences at the point of fecundation, where there
is formed a sort of minute crater, and thence passes entirely around the
yolk. In eggs that are quite mature and fresh, these changes succeed
each other with such rapidity that all spermatozoa which are a few
seconds behind the first are debarred access to the vitellus. Fol ex-
presses the opinion that normally fecundation is accomplished in the
starfish by a single spermatozodn ; with the sea-urchin this fact is evi-
dent. The point of penetration becomes the centre of a male aster; in
the middle of which a mass is formed (the male pronucleus) which fuses
with the female pronucleus as in the case of the sea-urchin. The
spermatozoén exercises an attractive influence at a distance, as well as
when in contact with the vitellus.
Toward the: close of the constriction which produces the first polar
globule in Nephelis, O. Hertwic (77) has observed that a small homo-
geneous area, surrounded by radially arranged yolk-granules, makes its
appearance in the half of the egg opposite the polar globule. This sub-
sequently takes a position in the centre of the egg, its radial system
having beeome more extended. After the second polar globule is formed,
this system becomes less distinct, and when the vacuoles make their
appearance in the semi-spindle lying under the polar globules, there
also appears at the centre of this central area a small vacuole. The
peripheral vacuoles unite into one, and then both peripheral and central
vacuoles, by the appropriation of nuclear fluid, become swollen to vesi-
MUSEUM OF COMPARATIVE ZOOLOGY. A81
cles of considerable size. By the migration of the peripheral vesicle
they come in contact, and become flattened against each other. After
treatment with acetic acid each appears to consist of a compact cortical
layer and of fluid contents which are traversed by netlike cords with
nodular swellings, and in which are found clusters of granules. This is
probably an artificial production, since in preparations made with osmic —
acid the nuclear contents remain homogeneous, and are only limited by
a somewhat firmer cortical layer. ‘Since these nuclei were not seen to
become confluent, —as is elsewhere (p. 328) more fully described, —
until evidences of the first segmentation appeared, Hertwig concludes
that the period of their confluence is of limited duration.
The following important conclusions are reached. The peripheral
nucleus arises from the granules of the lateral zone of thickenings, as in
ordinary cell-division, inasmuch as these granules are by the reception
of nuclear fluid converted into vacuoles, which ultimately become fused.
Therefore these vacuoles are not so many isolated nuclei (as Biitschli
thinks), but the component elements of a single nuclear structure.
But, as the spindle was derived from the nuclear substance of the ger-
minative vesicle, it follows that there exists an uninterrupted connection
between the several generations of nucler from the germinative vesicle to the
nucleus of segmentation. The direct evidence of the origin of the isolated
stellate figure is wanting, but from analogy with Toxopneustes there is
reason to believe that it is produced by the nucleus of a spermatozoin
which has penetrated the yolk. Therefore the segmentation nucleus 7s
derived from the conjugation of two sexually different nuclei; a female
nucleus, descended from the germinative vesicle, and a male nucleus, derived
from the body of a spermatozooén.
Finally, the formation of the polar globules takes place before fecun-
dation, since the latter is really accomplished only when the confluence
of the male and female nuclei takes place. This coincides, moreover,
with Strasburger’s studies on ‘canal cells.” Whether the pinching off
of these globules may not be affected by the act of aes cannot
be so positively answered.
After artificial impregnation the eggs of the frog all exhibit, according
to Hertwig, a change at the pigmented pole, which is readily distinguish-
able with a hand-lens. The middle of the dark field appears clearer and
yellowish, as though veiled in a layer of unpigmented substance. This
is really a thin layer of finely granular substance (with uneven surface
and thickest at its middle point) which closely resembles the contents of
the germinative vesicle in its last observed stages. There are in it also
VOL. VI.— No. 12. 31
482 BULLETIN OF THE
“ Dotterplittchen” and fine pigment balls. He concludes that this veil
is really composed of remnants of the germinative vesicle, eliminated
from the yolk by the contraction of the protoplasm after the dissolution.
and distribution of the substance of the vesicle, and of portions of the
yolk substance. But there is no ground for a comparison of this with
the formation of polar globules. His own observations do not prove
whether this elimination may ensue without fecundation. On eggs
hardened about an hour after fecundation there may be observed, at one
side of the centre of the dark field, near the margin of the veil, a “ pig-
mented process” extending obliquely into the yolk toward the middle
of the egg. The inner end of this projecting mass is swollen, and em-
braces a clear, finely granular substance which differs from the rest of
the yolk. About this clear spot the pigment grains are radially ar-
ranged ; within it is a nuclear structure of much the same nature as the
pronuclei already described. This nucleus grows rapidly as the dark
process lengthens toward the axis of the egg, which it finally reaches
two thirds of the way from the surface to the centre of the yolk. Mean-
while a similar nuclear structure is seen near this axis in the opposite |
half of the egg; it is not, however, surrounded by pigment, but lies in
the yolk, from which it can be distinguished only with difficulty. Sub-
sequently both nuclei lie in the swollen end of the pigmented process,
and fuse into a single nucleus which now lies immediately surrounded
by a layer of finely granular protoplasm which is in turn enveloped in
the swollen end of the pigment process. This requires only about two
hours and a half from the time of fertilization. The interpretation
which Hertwig gives these observations is too evident to require their
formal statement. Never was more than one ‘ pigment process ” observed,
so that the penetration of only a single spermatozo6dn is probably normal.
The most important fact established by Hertwig, and one entirely
new for Batrachia, is the existence of an “egg nucleus” which ulti-
mately unites with the “sperm nucleus.” Concerning the origin of
the former, Hertwig says, it is quite probable that so inconspicuous a
structure should have existed and been overlooked before the stage at
which he first saw it. From its minuteness it certainly cannot corre-
spond to the total mass of nuclear substance contained in the germina-
tive vesicle; that, however, does not prevent its having descénded
directly from such nuclear substance. The problem here is not, after all,
why so little nuclear substance is transferred to the female pronucleus
(Eikern), but what signification has the mu/¢/nucleolar, as compared with
the wninucleolar condition of the germinative vesicle 4
MUSEUM OF COMPARATIVE ZOOLOGY. 483
In the “General Part” of this paper Hertwig considers, among other
things, the grounds for maintaining the morphological identity of the
“«Spermakern” with the body (nucleus) of the spermatozoén, rather
than the dissolution of the spermatozodn and subsequent re-collection of
its substance into a male pronucleus, as held by Ed. van Beneden and
Strasburger. They are :—
1. In the conifers the possibility that the fine membrane of the apex
of the pollen tube is partly dissolved away, cannot be excluded.
2. In Hirudinea, mammals, etc., the vitellime membrane can present
no obstacle to the penetration of spermatozoa, inasmuch as many have
been observed within the membrane.
3. A difference in size between the Spermakern and the body of the
spermatozodn is not evidence against their identity, since the former is
by direct observation known to increase in size before copulation with
the egg nucleus.
4. In Toxopneustes there is an interval of only a few minutes between
the time of artificial fertilization and the appearance of the sperm nu-
cleus. It is improbable that a solution and re-formation takes place in
this short interval, nor is there any motive to such an zndirect procedure.
5. The existence of a fine filament seen in Toxopneustes to extend
from the sperm nucleus beyond the periphery of the egg, which is to be
interpreted as the cilium of the spermatozoon.
Pérez (77) gives in a note the results of his attempt to verify on
Echinus esculentus Fol’s recently published account of the phenomena
of fecundation. In two cases he observed the protuberance of the sur-
face of the egg, which Fol considers due to an “attraction 4 distance ”
exercised by a spermatozoon, but is unable to attribute to it the least im-
portance. In one case there was no spermatozoon facing the elevation ;
in the other, a spermatozoon, after remaining immovable for some seconds
in the middle of the thickness of the mucous layer, advanced actively
to the summit of the elevation ; but there was no delicate prolongation
of the elevation toward the spermatozoon, nor did the latter glide into
the yolk, — it remained fixed at the surface. Scarcely was this effected,
when a second, following the same course as the first, traversed the
mucous layer “with two or three leaps,” and joined the surface of the
minute elevation. Two others followed, but reached only the middle of
the layer. Neither of the first two entered the egg, but with the eleva-
tion of the previously existing vitelline membrane, which soon followed,
were borne a considerable distance from the yolk, which was, neverthe-
less, now fertilized.
484 BULLETIN OF THE
Pérez endeavors to explain Fol’s observations by supposing that the
head of the spermatozoén, being a little higher or lower than the pro-
tuberance which occupied the focal plane, was ‘“ projected” upon the
latter, and was thus made invisible, while the cue remained distinct. (!)
This protuberance of the yolk, says the author, has nothing to do
with fecundation. It is simply an accident depending solely on an in-
terruption in the continuity of the mucous envelope, which thus forms
a point of least resistance at the surface of the egg, and therefore a cor-
responding deformation of the yolk. Such a penetration is, moreover,
an anatomical impossibility, on account of the existence of a vitelline
membrane from a very early stage of egg development.
Fou (’'77°) communicates interesting results concerning abnormal
fecundation in the starfish, and deduces from them important conclu-
sions. Ifthe spermatozoa are brought into contact with eggs before the
formation of the first polar globule, the vitelline membrane is formed
and detached only very slowly around the point where the first sperma-
tozoon penetrates, and extends over only a fraction of the surface, so
that other spermatozoa continue to effect an entrance, until finally the —
joint result is a continuous envelope. The extent and rapidity with
which this membrane is formed are proportional to the nearness with
which the normal conditions are approached. The deportment of the
individual spermatozoa is the same as in normal cases. The nearest
male pronucleus unites with the female pronucleus, which becomes at
once the centre of a system of radial filaments. The resulting “ noyau
combiné” unites with a second, or even a third, male pronucleus. At
other times the female pronucleus, at the moment of its formation, sepa-
rates into two or three fragments, which unite with as many male pro-
nuclei. The male asters never unite with each other; they appear to
repel each other, and to be attracted by the female pronucleus up to the
time when the latter has been neutralized by union with two or three
male pronuclei. When there are numerous male centres, the vitellus in
its segmentation forms at once a like number of rounded elevations, —
each with a male aster in its centre, — which become little spheres and
continue to divide dichotomously. Thus the cleavage process is irregu-
lar, and there results an irregular blastosphere and a monstrous larva.
When the male pronuclei are limited in nimber and the female pro-
nucleus is divided into two or three, the latter remain distinct. At the
moment of cleavage each is converted into an amphiaster and the vitel-
lus is divided at once into four or six spherules. Cleavage was never
observed when the single nucleus resulted from the union of several
MUSEUM OF COMPARATIVE ZOOLOGY. 485
male pronuclei with the female pronucleus. A nucleus may be resolved
at once into a ¢etraster, — four asters united to each other. A vitellus
which has received two spermatozoa was never seen to develop normally,
but always produced double the normal number of spheres.
Analogous phenomena (the penetration of numerous spermatozoa) are
observable with eggs fecundated at maturity, if they have come from
diseased animals. The bodies of the spermatozoa in this case remain
intact within thé vitellus, although surrounded with faintly expressed
radial striations. As their bodies are never found intact except in
these abnormal cases, Fol concludes that the male centre is produced
by the fusion of the ‘“‘body” with a little vitelline protoplasm. The
mutual repulsion of the male centres he considers to be a corollary of
their attraction for the female centre, just as the mutual repulsion of
the poles of an amphiaster is a corollary of the attraction they exert
on the surrounding protoplasm. j
When the spermatozoa of Psammechinus miliaris come in contact
with the egg, their heads are, according to GiarpD ("77"), applied to the
whole periphery of the membrane (vitelline?), and they impart to the
sphere a very rapid gyratory motion. The vitelline membrane, hitherto
very near the surface of the yolk, gradually separates from it, and con-
sequently the second ‘“‘cumulus” (see p. 444), whose summit adheres to
the membrane, is drawn out into a cone connecting membrane and
vitellus. As no spermatozodn is seen to penetrate into the vast clear
space which now intervenes between membrane and yolk, the author
believes that this cumulus serves for the passage of a spermatozoon ;
either that its summit corresponds to a pore in the membrane, or, as is
more likely, that the act of fecundation consists essentially in the difiu-
sion of male protoplasm through the membrane at the point where
the latter is in direct contact with the female protoplasm, i.e. at the
summit of the cumulus. ‘This connecting cone soon detaches itself from
the membrane, and re-enters the vitelline mass. The male pronucleus
which results is not said to induce a stellate figure. The nucleolus of
the male pronucleus Giard thinks cannot be the unmodified head of the
Spermatozodn. He is inclined to believe that the gyratory motion im-
parted by the spermatozoa facilitates the advance of the pronuclei
toward the centre of the yolk, since eggs for some time stationary are
developed irregularly. How this rotation facilitates the migration is
not stated by the author. 7
In Fou’s (77°) illustrated paper on the “Commencement of Heno-
geny,” etc., it is stated that the gliding of the body of the spermatozodn
.
486 BULLETIN OF THE
into the vitellus resembles the flow of a viscid liquid. The successive
forms assumed by this lengthened “body” vary greatly in different cases,
and change rapidly. It continues to diminish in size until there remains
only a filament presenting varicosities and surmounted by a motionless
cue. Some seconds later this latter has in turn disappeared, and one
sees in its place only a very pale elongated cone. This is an exudation
from the vitellus; but the vibratile cilium (cue) in process of decom-
position may contribute to its formation. This “cdne d’exsudation”
remains visible several minutes, and assumes the most diverse forms,
recalling the flames of a feu de paille, though not as rapid. Sometimes
it is simply conical ; sometimes nodulated and flanked by barbules and
tongues. Ic finally disappears (pp. 459, 460). The rays of the male
aster commence to be distinctly visible only some minutes after fecun-
dation, and then the clear spot is already advanced a little toward the
interior of the yolk. Some of the rays extend back to the surface
where the contact took place, and where a minute scar still remains.
Fol thinks O. Hertwig has mistaken such rays for a part of the tail of a
spermatozoon. ‘The female pronucleus commences to move toward the
male pronucleus only when it comes in contact with the rays of the
male aster (pp. 463, 464).
Statements relating to the fecundation of the eggs of Heteropoda —
are mentioned (p. 446) in connection with the review of their matu-
ration.
BiscHorr (’'77, pp. 28-48) defends his theory of fecundation, as a
communicated molecular motion imparted by the spermatozoodn to the egg,
from the misinterpretations which he holds it has suffered at the hands
of those critics who could see in it only a “ Contactwirkung.” <A mate-
rial participation on the part of the spermatozoén does not appear to be
denied, but is valueless in the author’s opinion to explain the actual
process of fecundation. ‘Was aber die raumliche oder formbildende
Wirkung des Saamens bei der durch ihn auf das Ei tibertragenen Be-
wegung betrifft, so ist diese an und fiir sich eine Thatsache, aber einst-
weilen eben nur eine Thatsache, fiir deren weitere Begriindung und
Erkenntniss bis jetzt auch nicht die mindeste Hoffnung besteht”
(p. 33).
Apropos to a comparison of the ectoplasm and endoplasm of Protozoa
and eggs, Minot (’77°) calls attention to the theory that “the Rich-
tungsbliischen are comparable to the nucleoli of Infusoria. A further
confirmation of this homology is offered by the formation of the ‘ Kern-
spindel’ as introductory alike to the ejection of the direction cells and
7
MUSEUM OF COMPARATIVE ZOOLOGY. AS7
the expulsion of the nucleoli.” * ‘‘We distinguish therefore equally in
both cases the formation of a generation in which the two sexes are separate
cells, and then the union of two sexual unicellular individuals, of different
origin, to form an asexual cell, which then goes on dividing asexually for
many generations until the original energy is exhausted.” The egg
really becomes female only upon the discharge of the male direction
cells. It is important to know whether in the development of the
spermatozoa the mother cell breaks up into two portions, one of which
becomes the male part, while the other remains separated. ‘‘ The few
available observations fulfil our expectations, for they describe a ‘ MZut-
terkern’ (female element) which remains behind and is aborted.”
In a provisional theory of generation McCrapy (’77) concludes that
the act of generation consists in the actual conjugation of at least two
protozodids (one ovum, and one, or in most cases several spermatozoa).
The result is twofold: (1.) the combination of the nucleus of the sperma-
tozoon with the germinative vesicle of the ovum (this resultant is the
future animal) ; and (2.) the aggregation of the yolk protoplasm with the
protoplasm of the spermatozoa, these together constituting a store of
foo for the immediate nourishment of the newly arisen animal, which it
proceeds to appropriate in the manner of a rhizopod. This appropria-
tion of the whole provision is the process called segmentation. It is
probable that in the conjugation the germinative vesicle and the sper-
matozoon (or its nucleus) disappear and cease to exist as such. In their
stead arises the new animal, or protembryo. This new animal may pre-
sent itself under one or the other of three conditions : (a) as a clear
mass of protoplasm within the yolk mass, —the embryonal vesicle of
_ Wagner ; (4) as a nearly uniform layer of protoplasm, completely enclos-
ing the yolk mass; or (c) as a combination of a and 6, in which the
central and peripheral portions of protoplasm are connected with radial
threads of the same. These are respectively styled Hnto-, Ecto-, and
Panto-protembryo.
With the fundamental correction now possible, that it is not the ger-
minative vesicle, but the female pronucleus, which unites with the sperm
nucleus, this view appears to approach that which Strasburger has more
recently promulgated ; but how far it comes short of a just appreciation
of the mutual relations of nutritive substance, living protoplasm, and
nuclear substance, is too apparent to demand discussion. There does
not seem to have been here, any more than in the paper last reviewed,
* The nature of the argument to be drawn from the ‘‘ Kernspindel” has been
stated by Whitman (’787, p. 46).
488 BULLETIN OF THE
an attempt made to contribute by special personal studies of the phe-
nomena to the solution of the questions considered.
In a preliminary note on fecundation, Fou (’774), beside communicat-
ing the substance of what has already been given, defends his conclu-
sions from the adverse opinions of Pérez and Giard. Giard’s view, that a
large number of spermatozoa are necessary (by the motion they impart)
to fecundation, is refuted, he claims, by his (Fol’s) method of artificial
fecundation, in which only two or three spermatozoa were allowed for a
single egg. The cases of abnormal fecundation prove that in the eggs
of this species the existence of a membrane with a micropyle cannot be
admitted. If there were a membrane, as Pérez and Giard assert, there
would have to be numerous micropyles.
The results communicated by O. HeErtwic ('77*) in a preliminary
paper will be considered in the review of the ultimate papers (O. Hert-
wig "78 and 78") at pages 495 and 509.
The act of fecundation in Serpula— as was also stated in his previous
work on the development of that animal — is, according to StossicH
(77, pp. 214, 217), external ; the spermatozoon does not enter into the
egg, but remains attached to its surface by means of the head, and not by
the tail. The substance of the mature spermatozodn undergoes a process
of transformation, by which its molecules are found in motion, which is
eventually shared by the material of the egg. The movement develops.
itself at first in the external layer of the yolk, in the form of a rotary
movement of the vitelline granulations, accompanied at the same time
by a chemical transformation of the fundamental material, by which new
granules are deposited and the material is rendered more opaque. In
consequence of these transformations, there is secreted the gas or liquid
previously mentioned by Stossich. (See p. 428.)
The discussions on the nature of fecundation in Echinodermata are
further continued in ‘Comptes rendus,” etc., by Fol on one side, and
Giard and Pérez on the other. The principal points under discussion
are: (1.) whether fecundation is effected by the penetration of a
spermatozoon ; (2.) whether there exists a vitelline membrane before
fecundation ; (3.) the nature of the vitelline protuberances called by Fol
“‘ cone d’exsudation ” and “ cone d’attraction.”
Fou (77°) responds by concluding that the negative results of Perez
and Giard are due to their having studied only eggs already fertilized, a
possibility he himself has carefully guarded against by the use of his
compressorium, wherein one may observe the eggs from the first instant
of the mingling of the two sexual products. Only three or four sperma-
MUSEUM OF COMPARATIVE ZOOLOGY. 489
tozoa, moreover, are allowed to a single egg. The protuberance which
Pérez has seen is not at all the hyaline cone, but is a granular projection
of the yolk of considerable size. Corresponding to the point of attach-
ment of the ovule there is an interruption in the continuity of the mucous
envelope, and into this the yolk often penetrates. This protuberance
is wanting in eggs near to exclusion. In the sea-urchins the process of
penetration is much more rapid than in the starfishes, and there 7s no
hyaline protuberance formed in this case. Hence the error attributed to
the author by Pérez is impossible, as regards the sea-urchins at least.
The pre-existence of a vitelline membrane is disproved by the author’s
preparations, still preserved; for when the polar globules are formed after
fecundation, they are found to be within the vitelline membrane, but
when before fecundation they are outside of that membrane. Fol does
not deny the existence of a limiting envelope at the surface of the ovule
in starfishes and sea-urchins, but it is soft and plastic, like the limiting
layer of an Ameeba. One can make of it a membrane by coagulating
the organism. This layer normally becomes a membrane only at the very
moment of fecundation.
Pérez ("77") is still unable to admit an attraction exercised “a dis-
tance” by the spermatozodn, for he has observed in the case of the
sea-urchin Fol’s “cone d’exsudation” before as well as after the approach
of spermatozoa, up to the time when the elevation of the vitelline mem-
brane and the expansion of the mucous layer have caused it to disappear;
but he regards it (the cone) as the optical projection of the walls of the
opening which constitutes the interruption in the continuity of the
mucous layer. The “soft and plastic layer” of the vitellus cannot be
compared to the envelope of the Amceba, since the spermatozoa after
traversing the mucous layer meet here an impenetrable obstacle.
Grarp ('77°) does not recognize the “necessity of employing sperma-
tozoa in homeceopathic doses,” since those conditions are not realized in
nature, nor does he understand how it is that Fol depicts eleven sperma-
tozoa on a limited portion of the surface of an egg, if in his experiments
he allows to each only three or four spermatozoa. From 10 to 15% of
the eggs he himself has studied present pathological peculiarities, among
“which are not included cases of the formation of a tetraster, which he
\
|
.
)
—— CO
considers due to an ontogenetic abbreviation, not resulting in monsters,
and comparable with Strasburger’s observations on gymnosperms. Fol’s
Statement that the sea-uwrchins present no hyaline protuberance is cer-
tainly not applicable to Psammechinus, where this protuberance is to be
Seen with the greatest ease. If Fol’s view concerning the vitelline mem-
490 BULLETIN OF THE
brane is accurate, the polar globules ought always to be found outside
the membrane in all cases of normal fecundation ; they are, on the con-
trary, applied to the vitellus so that they are difficult of observation.
Fou ('77/) responds to Giard by saying that in the sea-urchins of the
Mediterranean which he has studied there does not exist the “ cdne
d’ attraction ” which zn the egg of Asterias vs formed in front of the most
advanced spermatozoén ; not a single hyaline protuberance appears on
the mature egg of these sea-urchins before fecundation.
The concurrent evidence of O. Hertwig’s and his own studies shows
that the polar globules are promptly detached from the ovule, not being
retained by any membrane, and are lost in the ovary. Fol finds very
small and pale corpuscles lodged inside the outer of the two vitelline
membranes which exist in the sea-urchin. There are usually more than
two, and as the globules described by Giard appear to correspond with
these, he concludes that this author has not observed the true polar
globules. Instead of traversing the supposed vitelline membrane by way
of diffusion, as Giard thinks, the body of the spermatozodn penetrates,
as such, the vitellus, a fact still demonstrable in his preparations.
Fou’s (77%) communication to the Swiss Society of Natural Sciences
in August contains, beside what has already been given, some points
which are not previously dwelt upon. In the starfishes there is only
one vitelline membrane formed, but in the sea-urchins a second mem-
brane is formed beneath the first, although it is not detached from
the surface of the yolk until the moment of the first segmentation.
In the third of the experiments here recounted, the eggs of the sea-
urchin were fecundated by mixing them in sea-water with very dilute
spermatic fluid, and then at once removed by a pipette to 2% acetic
acid, followed successively by osmic acid and Beale’s carmine. All
these eggs have at one point of their surface a membrane raised up
in the form of a watch-glass bulging in the middle and continuous at its
margin with the limiting membrane of the yolk. At the centre of the
region covered by this membrane the body of a spermatozoén is im-
planted in the surface of the yolk by its point. It lies in the direction
of the radius of the egg, and has a cue. In eggs hardened a little
later the body of the spermatozoon, recognizable by its shape and the
color imparted by reagents, is sunk completely into the yolk so that its
blunt end is “flush” with the surface. In place of the cue is a vest
cle attached to the spermatozodn on the one hand and to the vitelline
membrane on the other. The latter is now elevated from the yolk on
all sides. A comparison with living eggs and those hardened simply in
MUSEUM OF COMPARATIVE ZOOLOGY. 491
osmic acid shows that the vesicle is the ‘‘céne d’exsudation” swollen
by the action of the acetic acid.
In the case of abnormal fecundation, where two or three of the male
asters have united with the female nucleus, the remaining male asters
are very regularly placed at equal distances from each other and at
about a third of the distance from the surface to the centre of the yolk.
This proves (1.) the attraction of the male asters for the female nucleus
up to the time of its saturation, and (2.) the mutual repulsion of the
male asters, for otherwise their arrangement, irregular at their first
appearance, would not subsequently become regular. Eggs that have
received two spermatozoa have always been seen to form a tetraster
instead of an amphiaster at the first segmentation. In certain cases of
sea-urchins kept a short time in confinement, a large majority of the
artificially fertilized eggs have exhibited the tetraster ; almost all the
larve were monsters. It is possible in certain vegetables, and even in
certain animals, that the tetraster may not be a pathological phenome-
non, but in the sea-urchin and starfish it is positively pathological as a
rule, and it is doubtful if such an egg can produce a normal larva.
Fou (’77") has also published a reply to the criticisms of Pérez and
Giard, which is more extended than any of the papers cited ; but since
it contains nothing essentially new, a review of it will be unnecessary.
Hatscuexk ('77*, pp. 503-505, Taf. XXVIII. Fig. 1) finds within the
pear-shaped egg membrane of Pedicellina (whether vitelline or second-
ary membrane is left unsettled) sometimes a small, sometimes a large
number (50) of active spermatozoa. This is evidence of the existence of
a micropyle. At the vegetative pole of an egg which had two polar
globules there was seen a clear protoplasmic body, free from yolk gran-
ules, which, in the course of two or three minutes, became lost to vision
by sinking into the yolk. Hatschek considers this a metamorphosed
spermatozodn ; but it seems probable that it should rather be compared
with similar hitherto unexplained protoplasmic protuberances from the
vegetative pole of the egg which usually occur after impregnation.*
A possible objection to this view exists in the fact that these pro-
tuberances are not always destitute of yolk granules, as Hatschek affirms
of the body he has observed ; but this may be subject to variation in
different cases.
HorrMann (77, p. 19) has observed in the case of Malacobdella that
the spermatozoa do not always penetrate the yolk with the head end,
but often bore in with the tail end, and continue in activity for an hour
* Compare Whitman "78%, pp. 21, 39, and O. Hertwig "78%, Taf. XI. Fig. 4.
492 BULLETIN OF THE
after fertilization. This account seems to need confirmation, for the
greatest care must be exercised to insure the observer against the possi-
bility of having before him eggs that are no longer in an active living
condition. Hoffmann has observed clear protoplasmic elevations on the
surface of the yolk, such as Biitschli has figured for Nephelis, but since
the same phenomenon is seen on eggs that have certainly not been
brought within the influence of spermatozoa, he thinks it cannot be
that it has resulted from a metamorphosed spermatozodn. It may be
considered as certain, he holds, that the penetration of the spermatozoa
and the subsequent lively motion of the yolk granules induce the grad-
ual disappearance and probably the complete elimination of the nucleus
(germinative vesicle), for on artificially fecundated eggs so many sper-
matozoa are sometimes attached to the yolk as to put it in rotation, and
in such cases the nucleus is ejected in its full size an hour after fer-
tilization, whereas normally, when only a few spermatozoa are attached
to the egg, the two small polar globules do not appear until’ two hours
after fertilization. (!)
In the case of Clepsine, Horrmann (77%, p. 34, Taf. III. Fig. 5)
seems to have seen something of the asters of the male and female pro-
nuclei. He has figured and described in a section of an egg prepared
several hours after extrusion, the existence of two places in the coarsely —
granular yolk which are filled with a finely granular substance, radially
arranged about the centre of each spot. :
In Toxopneustes variegatus SeLENKA ("78) has observed the penetra-
tion of spermatozoa of which he gives this account. Usually only one
spermatozoon succeeds after a long boring motion with its pointed head —
in passing through the jelly-like zone which envelopes the egg. As soon
as it gets near the yolk it is suddenly enabled to swim rapidly and
easily in all directions over the plasma mantle which envelops the yolk
(see p. 458). The passage it has made through the zona remains open
and is often traversed by both inward- and outward-going spermatozoa.
The spermatozodn usually penetrates the yolk at the “ Dotterhiigel,”
and causes a distinct agitation in the surrounding parts by its boring
motion. A tufted’ mass of clear substance at once collects around the
head of the spermatozodn from the clear mantle of protoplasm which
surrounds the egg. As it penetrates deeper into the yolk this tuft of
protoplasm sinks with it; thus forming a depression from the middle
of which the “tail,” which soon becomes motionless, projects as a fine
filament. When it has penetrated about a quarter of the way to the
centre the automatic motion almost instantly ceases, and within half a
MUSEUM OF COMPARATIVE ZOOLOGY. 493
minute there is formed around the “head” the well-known stellate
figure. In the course of a few minutes the ‘‘ head” advances to the
centre of the egg and remains there till the arrival of the egg nucleus.
Meanwhile the rays increase in number and in length, and at the same
time a ‘clear area,” formed by the accumulation of protoplasm free
from granules, makes its appearance at the centre of the system around
the “head” of the spermatozoén. The “neck” of the latter gradually
swells until it attains one third the diameter of the egg nucleus. The
highly refractive tip of the spermatozoon is meantime thrown off and
borne away by the ever-active yolk protoplasm ; like the tail, it is ap-
parently resorbed.
It always appeared as though a gentle amceboid motion of the egg nu-
cleus begah only at the moment when the rays surrounding the sperm
nucleus had extended to it, as though it were thereby induced to begin
its migration to the centre of the egg, along the course marked out by
these protoplasmic rays. But in any event an automatic amceboid mo-
tion of the egg nucleus must be maintained. If it is granted that
definite courses for the streaming protoplasm are present in the yolk, (of
which, however, nothing is known with certainty,) it is not evident how
the nucleus could be urged into the centre of the yolk by such currents
of protoplasm, since the masses of the latter moving in centrifugal and
in centripetal direction must be equal, and since the egg nucleus would
therefore receive the same impetus in opposite directions.
A direct union of the two nuclei follows, and is accompanied by very
active changes of form on the part of the egg nucleus, which sends out
thick pseudopodia-like projections enveloping the ‘Spermakern,” and
then suddenly fuses with it.
As soon as the point of the head of the spermatozoén has penetrated the
plasma mantle of the yolk there is raised up from the latter (within two
minutes) a fine membrane, which pushes before it the zona and absorbs
by diffusion the now fluid substance of the latter. In five minutes the
membrane is far removed from the yolk, and the zone is no longer
visible.
The spermatozoa may penetrate the yolk at any other place than the
“Dotterhiigel” -without influencing the subsequent development, which
also continues to go on for a time in a quite normal manner, when
two, three, or even four spermatozoa at one time, or in quick succession,
penetrate the yolk at the ‘“ Dotterhiigel,” or at different places on its
surface. In this case each “head” acquires independently its radial
figure. The author does not, in view of the observations of Fol and
494 BULLETIN OF THE
Hertwig, place much confidence in this observation of normal develop-
ment after such fecundation. A fusion of sperm nuclei is not to be
seen ; on the contrary they are mutually repelled by their astral rays.
Extensive studies on the nature of fecundation among plants lead
STRASBURGER ("77) to a modification (p. 483) of his previously expressed
views,* for he now holds that not all of the contents of the pollen tube |
are taken up by the egg nucleus, but that a part of it becomes directly
mingled with the protoplasm of the egg. It now appears improbable
to him that the portion of the fecundating substance which is destined
for the egg nucleus can be appropriated by the latter in the amorphous
condition in which it enters the egg, without having first assumed the
form of a nucleus. This view is then generalized and sharply formulated
(p. 508) as follows: “It is the equivalent parts of both cells which are
united in fecundation.” Support is afforded this view by the process of
copulation in the “Gameten” of Acetabularia and Spirogyra, in the
conifers, and especially in the case of those metasperms whose egg
nucleus contains only a single nucleolus, and where the sperm nucleus
in like manner embraces only a single nucleolus. For he finds that in
such cases (e. g. Monotropa, pp. 488, 489, Taf. XXX. Figs. 127-129, 131-
133, 135, 138) the new cell nucleus (male pronucleus) and the egg nucleus
unite without the disappearance of their nucleoli, so that two nucleoli,
which ultimately unite, are distinguishable for a considerable time within
the conjugated nuclei. This is the more noticeable in the case of Mono-
tropa from the fact that the male pronucleus and its nucleolus are
constantly somewhat smaller than the corresponding egg nucleus and
nucleolus. The division of the pollen cell shortly before fertilization,
from which result a greater and a smaller (“vegetative”) cell, is found
by Strasburger to hold true with metasperms (p. 450) as well as with
archisperms. With the formation of the pollen tube the nuclei of both
migrate—the nucleus of the large cell foremost — usually into its tip
(p. 456), where they take part in fecundation. But in the archisperms
the “vegetative” cell is resorbed while the nucleus of the larger cell
migrates to the tip of the pollen tube and there undergoes successive
divisions, — two or more. The tip of the pollen tube is never broken
through. Its protoplasmic contents are thought (pp. 483, 490) to pass
both the membrane of the pollen tube and that of the embryo-sac,
not in a diosmotic way, but directly, as a homogeneous viscid mass.
The same force which has impelled the protoplasm during the growth of
the tube toward its tip now causes it to advance in the direction of (i. e.
* See Strasburger "76, pp. 308, 309, and "76%, p. 402.
MUSEUM OF COMPARATIVE ZOOLOGY. 495
into) the embryo-sac. The author thinks this assumption is supported
by certain results obtained by Maxime Cornu (Comptes rendus de |’ Acad.
des Sciences, Paris, Tom. LXXXIV. p, 134). Of the two nuclei which
are found in the tip of the pollen tube at the beginning of fertilization,
the one in the rear (from the “vegetative” cell) is the first to disappear.
For this reason Strasburger says it may be that it is the substance of the
other nucleus which is more especially concerned in the act of fecundation
(p. 487), its substance being preserved in a nuclear form up to the very
instant of fecundation. The homogeneous condition here brought about
just before fecundation by the disappearance of every nuclear structure
makes the fecundation of phanerogams in a sense parallel with that of
the higher cryptogams where the spermatozoid, though a “formed”
structure, has no nuclear differentiation, but is a homogeneous band in
which the nuclear substance is probably distributed uniformly. In
plants where the copulating elements remain in an indifferent condition,
i. e. indistinguishable from each other, there may be more than two
such individual elements concerned in the act (e. g. Spirogyra, etc.).
With a differentiation of the sexual products the possibility of this ap-
pears to cease.* Why in general only one spermatozoid is admitted to
an egg, remains undecided. In the case of plants it may be owing to
the extremely rapid production of a cellulose envelope, yet molecular
processes of an altogether different character may in this case come into
action.
The experiments of Fol and O. Hertwic (’78) in the fecundation of
starfish eggs are in many ways mutually confirmatory. In others their
opinions differ. According to Hertwig eggs that are fertilized any time
between the formation of the first maturation spindle and the completion
of the egg nucleus afford evidence of the penetration of only a single
spermatozoon ; but there is this difference in the two cases. When the
fertilization takes place at the earlier date, the male and female pronuclei
attain equal size before their confluence, although the male pronucleus
remains comparatively small and with little influence on the surround-
ing protoplasm up to the time the second polar globule is formed. On
the other hand, when fertilization ensues only after the formation of the
egg nucleus, the male aster grows rapidly in size, but the male pronucleus
remains a much smaller structure than the female. Hertwig explains
this by supposing that in the latter case the female pronucleus has be-
* I do not understand how the observations of the author necessarily exclude the
nucleus of the ‘‘ vegetative” pollen-cell from participation in the act of fecundation ;
and if not excluded, the above sentence does not seem entirely justified.
496 BULLETIN OF THE
come possessed of all the available nuclear fluid of the yolk ; that in the
former they imbibe this fluid to the same extent. These two experi-
mental cases he maintains will serve to explain differences which exist in
different groups of animals. In these cases both of which are considered
normal, the yolk promptly retracts from the vitelline membrane after
impregnation, and one often sees a minute bridge of protoplasm connect-
ing the surface of the yolk with the membrane near the vegetative pole,
—probably the place of penetration of the spermatozoon. If the impreg-
nation is undertaken either before or after the epochs mentioned, ab-
normal phenomena are the result. The yolk withdraws from the vitelline
membrane not at all, or only slowly. A number of isolated stellar figures
appear in the cortical portion of the yolk, and remain limited in extent.
If the fertilization is effected during the metamorphosis of the germina-
tive vesicle, the development proceeds normally to the end of the forma-
tion of the polar globules, but not further ; if it is effected too late (six
hours after exclusion) two or three of the male asters may approach
close to the egg nucleus, and the latter sometimes takes an oval form.
Normal segmentation does not follow in either of these cases.
Hertwig disagrees with Fol as to the formation ofa vitelline mem-
brane at the time the spermatozodn penetrates the egg. The vitelline
membrane, he claims, already existed, and the interval between it and
the yolk is brought about by the contraction of the latter, which is
accompanied by the pressing out of the perivitelline liquid already ob-
served by the older naturalists.
The results which CatBerta ("78) has reached in his recent paper on
the fecundation of the eggs of Petromyzon Planeri he has himself con-
densed into the following form (p. 477). A single spermatozoén enters
through the outer micropyle into the space between the egg membrane
and the yolk. This space is filled with protoplasm free from yolk gran-
ules. The contact of the spermatozoodn with this sets in activity a
stimulus which results in a slight contraction —an amceboid motion —
of the yolk, which makes itself apparent in a separation of this clear
layer from the egg membrane in the vicinity of the micropyle. This
partial separation of the egg membrane from the yolk now makes pos-
sible an influx of water into the perivitelline space thus formed. Such
an inflowing of water was previously prevented by the pores of the egg
membrane being sealed up by the peripheral layer of clear protoplasm.
By this influx of water the egg membrane is widely separated from the
yolk. Authors who ascribe the existence of a great space between the
vitellus and membrane in lower vertebrates to an extensive contraction
ee ee Se ee ue eg a ee
MUSEUM OF COMPARATIVE ZOOLOGY. 497
of the former, are in error; the yolk suffers only a minimum contrac-
tion, and that occurs in the vicinity of the micropyle. This he has
demonstrated also in batrachians and bony fishes. Inasmuch as the
peripheral layer of protoplasm adheres in places to the egg membrane,
the protoplasm is drawn out, by the invasion of the water, into fine
threads connecting the surface of the yolk to the membrane. These
ultimately rupture, one end going to form drops on the inner surface of
the membrane, the other, elevations at the surface of the yolk. At the
micropyle a much thicker cord of protoplasm — the guiding cord of the
spermatozodn (Leitband)—has the same connections. It is through
this ‘‘ Leitband” of protoplasm that the head of the spermatozodn pene-
trates to the inner micropyle,* and thence into the sperm passage, and
thus reaches the egg nucleus. Calberla furnishes only very unsatis-
factory evidence that the head of the spermatozoon actually advances
to the egg nucleus. In sections of hardened eggs he has sometimes seen
in the sperm passage an indistinct elongated structure, which he would
refer to the head of the spermatozoon. The actual conjugation of two
nuclear structures cannot be claimed to have been observed. While a
part of the “ Mittelstiick” of the spermatozodn may enter the sperm
passage, its tail, he asserts, does not enter the egg but remains to plug
up the micropyle, and thus prevent the passage of other spermatozoa.
With the further removal of the egg membrane from the yolk this
cord of protoplasm (Leitband) is severed ; its peripheral end forming a
great drop on the inner surface of the membrane at the “outer micro-
pyle”; its central end forming a “ Dottertropfen ” in front of the inner
micropyle. Usually this ‘“ Dottertropfen” is drawn for a short time
within the yolk, only to appear again in consequence of a contractile
process within the egg which is connected with a stellar arrangement of
the yolk granules.
Concerning the egg nucleus during the penetration of the sperma-
tozoon, Calberla (p. 465) says it is altered, it becomes indistinct, but it
does not lose its morphological identity.¢ It is during this loss of dis-
tinct contour that the yolk granules arrange themselves in rays around
the disappearing egg nucleus. Subsequently one sees in its place a new
nucleus, with sharp contour, which he identifies with Hertwig’s “ Fur-
chungskern.” As soon as this segmentation nucleus is formed, the con-
traction of the yolk ceases and the “Dottertropfen” retires into the
* Compare the review (p. 456) of the maturation phenomena as described by Cal-
berla for Petromyzon.
t “Jedoch nicht zu Grunde geht.”
VOL. VI. — No. 12. 32
498 BULLETIN OF THE
yolk of the sperm passage. This marks the termination of the act of
fecundation.
If Calberla’s explanation of the reappearance of the “ Dottertropfen ”
is correct, this structure affords a very important index, — easily recog-
nized in the living egg,— not only to the tame at which the contraction
takes place, but also to the energy with which it acts at any given instant.
Calberla has further described this process of contraction as an arrange-
ment of the yolk granules concentric to the egg nucleus, which makes its
appearance at once upon the accomplishment of the nuclear copulation.
As the stages of copulation can hardly be said to have been satisfactorily
observed, it follows that the most which can be justly claimed is that
this stellate arrangement is to be observed about the time of the sup-
posed copulation. If Calberla is right in the interpretation of the elon-
gated body “Spk(?)” indicated in his Fig. 8 as a sperm nucleus, then
it is clear the radial arrangement precedes nuclear copulation and has the
egg nucleus for its centre, as he himself in one place clearly indicates.
Even if fertilization does not take place, the egg membrane after a
time — twelve hours if the eggs are maintained in cold running water
(+-8° to +10° C.), sooner if in warmer water — is elevated from the
yolk. But whereas in the former case this elevation began around the
micropyle and ensued next at the micropyle and only secondarily, as it
were, over the rest of the yolk, in the latter case it takes place slowly
and uniformly over the whole surface and without definite relation to
the micropyle. Moreover, in the latter case neither threads of proto-
plasm nor a “ Leitband” are formed. Although a “ Dottertropfen ” ap-
pears at the inner micropyle, it is not withdrawn into the yolk and
subsequently made to protrude, but ultimately ruptures and is soon
followed by the disintegration of the whole yolk. From the moment of
the first appearance of the elevation of the egg membrane, even if over
only a limited area, the egg becomes incapable of fecundation. How far
a possible change in the condition of the superficial clear layer of proto-
plasm might interfere with the penetration of spermatozoa could not be
established, as the latter were never seen in these cases to reach the
perivitelline space formed by the elevation of the egg membrane. The
existence of a “ Dottertropfen” in unfertilized eggs Calberla endeavors
to explain by assuming that the inflowing water exercises on the yolk a
stimulating influence which induces a slight contraction and consequent
protrusion of part of the contents of the sperm passage.
In a short supplement to his paper Calberla compares this “Leitband”
with the conical elevation observed by Fol in the case of Asteracanthion,
MUSEUM OF COMPARATIVE ZOOLOGY. 499
and by way of inference makes its existence due to an attractive influ-
ence exercised, at a distance (?), upon the yolk by the spermatozoon.
He thinks that there is no vitelline membrane formed in the case of
Petromyzon at the time of fecundation, such as Fol has described for
Echinodermata.
It remains to add that the phenomena of fecundation transpire more
rapidly the longer the egg has been removed from the animal, provided
it has not meantime suffered the change described above as occurring at
the expiration of about twelve hours.
Batrour ('78") has given a short synopsis of fecundation as observed
by Fol, 0. Hertwig, Selenka, Giard, and Calberla. He suggests that the
pathological symptoms shown in the embryos reared by Fol and Hert-
wig may be due to an imperfection of the eggs, induced by a delay in
impregnation, rather than to the entrance of more than a single sperma-
tozoon.
In his paper on “ Befruchtung,” etc., Von JHERING (’78) treats, for the
most part in a purely objective manner, of the recent discoveries in
maturation and fecundation of animal ova. He emphasizes (p. 121) the
fact that no morphological difference exists between nucleus and pro-
nucleus. The acceptance of the idea of a pronucleus, in view of the
parthenogenetic development of the starfish, is only possible with
the reservation that the female pronucleus does not necessarily need
the accession of a male pronucleus in order to become a segmentation
nucleus.
The final paper by SexenKa (’78%) on Toxopneustes variegatus, be-
sides contributing minor additional details concerning fecundation, con-
tains essential modifications of the preliminary notice. In the first
place, the union of the two pronuclei is not accomplished quite so
promptly as at first supposed. The first contact only results in a weld-
ing which lasts about fifteen minutes, during which the male pronu-
cleus grows until it reaches the size of the female pronucleus. During
all this time, the boundary between the two remains distinguishable.
It seems to have been previously mistaken by Selenka for the beginning
of the spindle differentiation. Finally, however, the limit between the
two pronuclei entirely disappears. .
He corroborates Auerbach’s observations of a rotation of the joined
pronuclei so far as to say that the long axis of the elliptical conjugation-
nucleus soon becomes oblique to the radius along which the spermato-
zoon penetrated. Whether this takes place only in the case where
the course of the spermatozodn is predetermined by the existence of a
500 BULLETIN OF THE
micropyle, or ‘ Dotterhiigel,” cannot yet be decided. He says he has
sometimes seen its rotation through 90° of arc, and adds, that “ there-
fore, since the spermatozoén as a rule penetrates at the ‘ Dotterhiigel,’
the first plane of division passes through that point (Dotterhiigel).
But inasmuch as the latter also indicates the place where the directive
corpuscles emerged, one may also say that the first segmentation plane
generally coincides with the radius which is determined by the long
axis of the nuclear spindle or by the course along which the directive
corpuscles emerge.” But,” he adds, “it is not to be forgotten that
the spermatic element may also penetrate at other places than at the Dot-
terhigel, and that then, not the ‘ Mikropylenhiigel,’ but the radius along
which the spermatozoin has penetrated would determine the direction of the
jirst cleavage plane.”
Resting on this argument, Selenka claims that it is not right to con-
sider that part of the yolk where the directive corpuscles emerge the
formative pole, and therefore that the name polar globules is not suit-
able for the directive cells of Toxopneustes.
I believe that Selenka is in error in saying that the plane of cleavage
is determined by the line along which the spermatazoén penetrates,
and think the protuberance called Dotterhiigel may be the source of
the difficulty. This the author has defined as the elevation left at the
place where the directive corpuscles escaped. He has doubtless ob-
served cases in which the first cleavage plane did not pass through this
elevation, and hence concludes there is not a constant relation between
the position of this plane and the place where the polar globules emerge.
Unless the identity of the Dotterhiigel and this place of emergence are
indisputably established, his conclusions will not necessarily follow from
his observations. |
I do not see that that there is any conclusive evidence that the
“ Dotterhiigel” may not be some other protuberance of the yolk than
that which was left behind by the polar globules; for example, such
an elevation as Giard has called the second cumulus, and which Fol
has affirmed to be a projection of the yolk imto a place of the
odlemma corresponding to the point of the ege’s ovarian attachment.
That this may really be the case here seems none the less probable
from the remark which Selenka (p. 6) himself makes, to the effect that
“the spermatozoa seem to penetrate the gelatinous mantle preferably
in the immediate vicinity of the ‘ Dotterhiigel,’ and that this is appar-
ently a more practicable passage, — it may be on account of the emer-
gence of the polar globules at this point, it may be because it is at
MUSEUM OF COMPARATIVE ZOOLOGY. 5OL
the same time the place where the pedicellate egg, up to a short time before
its liberation, was connected with the ovarian wall, and that therefore the
mantle is here softer.” The fact that the absence of a membrane allows
the polar globules to lose entirely their connection with the yolk, makes
such a mistaken identification as I have suggested extremely easy, or
at least would make the proof of the accuracy of the identification at-
tainable only by continuous observation of the same egg. If Selenka’s
erounds for disconnecting the polar globules and the position of the first
cleavage plane are insufficient, those for connecting the position of the
plane with that of the radius along which the spermatozoon penetrates
are limited to the statement of the fact, and therefore lie beyond the
reach of criticism.*
If those of Selenka’s conclusions which I have criticised should prove
to be untenable, the objections which he urges against the use of “ for-
mative pole” and “ polar globules” in Toxopneustes would be no longer
valid.
While Kuprrer uND BENECKE ("78) confirm the most interesting point
of Calberla’s observations on Petromyzon, — the penetration of a sper-
matozoon into the yolk,—they differ in many points of importance.
The micropyle is not always situated at the summit of the watch-glass-
shaped portion of the egg membrane. Only the znner layer of the egg
membrane is provided with pore canals, not both layers, as Calberla
claims. The cap of clear protoplasm which lies immediately under the
watch-glass area of the membrane is not continued as a thinner layer
around the whole yolk, but has about the same extent as does the watch-
glass elevation. Only those spermatozoa which attain the hyaline dome
(A. Miiller’s “ Flocke”) surmounting the watch-glass segment of the egg
membrane are of concern in the act of fertilization. All such at once
assume a direction radial to the ‘‘ watch-glass,”’ and as soon as the first
has reached this dome the yolk begins to withdraw from the egg mem-
brane, leaving an annular space corresponding with the rim of the watch-
glass. The contraction of the yolk therefore results from the influence
of the spermatozoa at a distance. This retraction is more lively if
several spermatozoa enter the dome instead of one. The further retrac-
* In what sense the spermatozodn radius is held to be ‘‘ determining” can pos-
sibly be inferred from an examination of his figures. From Figs. 16 and 17 it ap-
pears that the first cleavage plane (if perpendicular to the long axis of the nucleus)
neither coincides with nor is perpendicular to this radius. Therefore, the only con-
clusion that seems possible is that the position of the segmentation plane is held to
be dependent on two factors, — one the direction of the spermatozoon radius, and the
other the extent of the angular rotation of the fusing pronuclei.
502 BULLETIN OF THE
tion of the yolk results in the formation of the protoplasmic filaments
and the “Leitband”; the latter, however, is not constant, nor does it,
when present, always serve to guide a spermatazodn ; on the contrary,
a spermatozoon may penetrate the membrane at any point of the
watch-glass, even near its margin. The term “Axenstrang” is substi-
tuted for “ Leitband,” as the function implied in the latter word can-
not be proved to exist. The foremost or ‘“ preferred spermatozoén”
enters the yolk im toto, not leaving any part of its tail behind, as Cal-
berla claims ; but as soon as the head has entered the egg membrane
the activity of the spermatozoon seems to cease, the tail becomes stiff,
and the whole is drawn onward. The head part becomes more and
more elongated, as it approaches the yolk. All other spermatozoa which
penetrate the “‘ watch-glass ” a greater or less distance do not thus cease
their activity, and in addition to the motion of the tail there seems to be
an amoeboid change in the outline of the head; a wave-like motion is
observed to pass forward along the head to its free end. If the head
has advanced near to the inner surface of the membrane, it sends for-
ward a fine filament, like a pseudopod, which traverses the interval ;
waves advance along this filament, which becomes swollen at the end,
and finally the swollen part becomes detached as a clear vesicle in the
perivitelline space.
The retraction of the yolk is due to an actual contraction of its sub-
stance rather than to an invasion of water as claimed by Calberla. The
contraction is of such a nature that at one time the half of the yolk occu-
pying the active end of the egg has the form of a truncate right cone,
while the other half retains its ellipsoidal outline. At this time, about
three minutes after the union of sperm and eggs, a mass of clear proto-
plasm (Calberla’s Dottertropfen) rises up in the centre of the truncate
surface, enlarges and extends till, in about three minutes, it reaches the
inner surface of the membrane, which, by its amceboid motion, “ it licks
eff,” and then with many changes of form it retires. By this process it
incorporates with it the vesicles which Calberla called “ Randtropfen,”
but which are not all of them the retracted ends of the protoplasmic
filaments left by the retiring yolk, for a part at least were formed by
the spermatozoa in the way above indicated. This ‘“ Dottertropfen,”
occasionally at least, also envelops unaltered spermatozoa which have
effected their entrance into the perivitelline space. It is not simply the
again protruded “ Leitband,” for it is occasionally absent, and when
present is of greater volume than the latter. This protoplasmic projec-
tion exercises an active supplemental rdle in fecundation. While to one
MUSEUM OF COMPARATIVE ZOOLOGY. 503
spermatozoén falls pre-eminently the function of fecundation, other sper-
matozoa may participate in the act through the active intervention of
this protuberance of hyaline protoplasm.
To explain these phenomena the authors assume that a body (Hikern)
in the yolk, which at the approach of spermatozoa enters upon a state of
activity, exercises an attraction both on the protoplasm of the yolk and
on the spermatozoa, which diminishes with the distance, but increases
with the mass, and that this body is movable in the yolk. The radially
arranged spermatozoa at the surface of the “ watch-glass” give the im-
petus to a change in the nearest protoplasm of the egg, by means of
which the [egg] nucleus is formed. ‘The first effect is the detachment
of the protoplasm from the ‘‘ watch-glass,” and the attraction of that
spermatozoon which meets with the least resistance. Since the attraction
of yolk and nucleus is to be considered as mutual, and as proportional
to the mass, and since the greater part of the egg lies on the side of the
eccentric nucleus toward the passive pole, it follows that the yolk will
communicate to the nucleus a motion toward its (yolk’s) centre. The
nucleus thus becomes further removed from the ‘“ watch-glass,” and its
attractive influence on spermatozoa diminishes. Therefore any sperma-
tozobn which might chance to follow the same (microyplar) radius as
the first one would be less strongly attracted, and thus may be explained
why as a rule only one spermatozodn passes the membrane through the
micropyle.
From the nature of their fertilization it was not possible for WHITMAN
(’78*) * to observe the penetration of spermatozoa into the eggs of Clep-
sine. A nuclear body, which he from analogy concludes is the male
pronucleus, makes its appearance usually about the time the second
polar globule is formed. It has also been detected before the formation
of the first polar globule. It is found near the centre of the egg before
the female pronucleus has receded much from the oral pole. The nature
of these pronuclei will be discussed farther on. During the formation,
or at least during the migration and conjugation of the pronuclei, re-
markable changes occur at the poles of the egg, which previous observers
had seen only from the surface and designated as “polar rings.” By
means of sections Whitmah was enabled to study the internal changes
which the substance of these rings undergoes.
About fifteen minutes after the second polar globule is formed a trans-
parent fluid substance begins to collect in a shallow groove which en-
circles the ora! (animal) pole, thus forming the first polar ring. At
* See also Whitman "79.
504 BULLETIN OF THE
first feebly expressed, this ring soon becomes well defined and has on
either margin a border of yolk substance that is destitute of yolk spheres,
but densely packed with fine granules, and appears whitish in reflected
light. This ring deepens and at the same time approaches the pole so
that a central cup-shaped mass of the yolk is nearly cut off from the
main mass, having only a slender stalk of connection, like the stem of a
goblet. At the same time the outer or equatorial margin of the ring
becomes denticulate, and its substance stretches out towards the equator
of the egg in the form of rays, — the “‘ring rays.” About ten minutes
after the appearance of the first ring a second one appears at the aboral
(vegetative) pole of the egg, but in narrowing upon the enclosed space it
does not dip so deeply into the yolk, and ultimately forms a superficial
disk with thickened margins. This also sends out “ring rays.” At the
approach of cleavage the ring at the oral pole is made to assume the
shape of a crescent by the movement of the cup-shaped mass of yolk
toward that side of the ring which is nearest the plane of the coming
cleavage. Both sets of ring rays become more and more feeble at the
approach of segmentation.
On sections it is seen that the whitish substance which appears on
the borders of the rings forms a continuous layer underlying them.
After they have assumed, the oral one the shape of a compact, well-
defined ring with nearly circular section, — the aboral one the shape of an
oblate spheroid, — the “ whitish” substance underlying and more or less
surrounding them is seen to plunge deeply into the yolk at about the
time the first cleavage amphiaster is forming. The substance of the
rings takes the same course toward the cleavage nucleus. In osmic acid
and carmine preparations the ring substance behaves in the same manner
as the substance of the “nucleus”; it is therefore ‘ probably nuclear
matter, or something very analogous.” The rings “ possibly contribute
some elements to the nucleus, which may either induce or stimulate the
molecular changes, which result in the formation of the primary cleavage
amphwaster.”
The interpretation which Whitman gives the small sharply defined
bodies occupying the centre of what he regards as the pronuclei is, as
he himself fully understood, radically at variance with the more gener-
ally accepted view. Most observers have considered the structures in
question, even though two or perhaps several in number, as the pro-
nuclei themselves, and the surrounding ill-defined plasmic substance as
a specially differentiated, or at least segregated, portion of the yolk
protoplasm. Whitman, on the other hand, holds this homogeneous
eS Ne ae me ay ———
}
}
MUSEUM OF COMPARATIVE ZOOLOGY. 505
plasm (“nucleoplasm”) to be, not yolk plasm, but the pronucleus
itself, and the bodies embraced in it to be pronucleoli, and by means of
this interpretation (which is of course extended to the subsequent gen-
erations of nuclei and their nucleoli) is enabled to avoid the contradic-
tory position in which Biitschli and others find themselves when they
endeavor to explain the existence of several nuclei in a cell without
thereby interfering with the essential character of the cell as a uninu-
clear structure. — |
It is to be remarked in the beginning, that Whitman saw only traces
of a nuclear plate in the archiamphiasters, and these were so uncertain
in character that they were entirely omitted from his drawings. This,
I think, will serve to explain why he has been less successful in tra-
cing the origin of the female pronucleus than some other observers
whose more favorable objects have proved very instructive on this
point.
Immediately after the appearance of the second polar globule a circu-
lar space directly below the latter, which appears in fresh eggs as a pel-
lucid spot, is found in eggs treated with osmic acid and carmine to be
filled with a very fine granular substance which has the lead-gray tinge
and the feeble staining capacity characteristic of the germinal vesicle
when similarly treated. This is the remnant of the archiamphiaster,
and is called the female pronucleus. It is without membrane, perfectly
homogeneous, and forms the centre of a radial system. On the inner
(or deeper) side of the female pronucleus there are subsequently to be
seen two small highly refractive corpuscles in close apposition, and to-
gether 10 in diameter. These are sharply defined, homogeneous, and
more deeply colored than the nucleoplasm. They are female pronucleol.
Whitman gives no positive information as to the origin of these pro-
nucleoli, whether they have a genetic connection with definite parts of
the amphiaster or arise as new structures within the nucleoplasm. The
male nucleus, which comes into view near the centre about this time,
presents the same appearance, with, however, only one pronucleolus.
Both pronuclei are surrounded with radial lines, and their longest axes
lie in the main axis of the egg. In later stages only one nucleus is
found, with its main axis oblique to that of the egg, but embracing
both the male and female pronucleoli. The radial lines are fainter.
Then this primary cleavage nucleus comes to lie a little eccentrically
towards the oral pole, and its axis is at right angles to that of the egg.
Its substance (nucleoplasm) is more strongly colored near the pronu-
cleoli than at the periphery. Later the pronucleoli have become larger,
506 BULLETIN OF THE
and are closely applied to each other. They are still sharply outlined,
but only slightly stained with carmine.
The cleavage nucleus becomes more elongate, and, to judge from his
Fig. 71, more sharply defined ; but the pronucleoli do not become fused
until the “nucleus” [central area] has assumed the spindle shape, nor even
until the first cleavage spindle begins to form. Whitman, it is true, does
not figure any stage in which the bodies in question remain intact
after the cleavage spindle begins to appear ; but I wish to call attention
to the fact that he says (p. 24) such is the case, for it seems to me an
important point in helping to prove the identity between the structures
which Whitman calls pronucleoli and those which I have called the pro-
nucler. I do not understand how this late coalescence of the bodies in
question corroborates the view that they are nucleoli rather than nuclei.
I can see a priort no reason why either a dissolution or a coalescence of
nucleolar structures should be delayed beyond the time when a like fate.
overtakes the nuclei; on the contrary, evidence is not wanting that in
the metamorphosis of the germinative vesicle, where there will be no
ground for disagreement as to the nuclear nature of the vesicle, the
nucleolar elements are often the first to undergo radical change. Out
of numerous cases I will cite only O. Hertwig (77%, pp. 277, 278) for
Pterotrachea. The case of the germinal vesicle, it is true, is not one
in which we have to do with the fusion of similar elements, yet when
we consider that the metamorphosis in both cases is one which leads
directly to the formation of the spindle, I think the justice of the com-
parison will not be denied. In Whitman’s opinion, “the size, structure,
chemical behavior, and destiny of these bodies ” favor his interpretation.
It is of course important to ascertain at first if the bodies in question
are really the same in the case of Clepsine and Limax. ‘There appears
little or no room to doubt this identity, notwithstanding their rather
striking differences of size, since, on the one hand, Whitman identifies
respectively his pronucleus and pronucleolus with the ‘ Strahlensys-
teme” * and the minute corpuscles embraced in the same, as described
for Nephelis by Biitschli and Hertwig ; and since, on the other hand, the
questionable structure in Limax, though ultimately far from minute,
* To assume that the radial systems are the nuclear structures (the pronuclei in
this case) seems to lead one into the unfortunate position of being compelled to
identify the whole, or nearly the whole, protoplasm with the nucleus, for the radial
systems at one time or another stretch through the entire yolk; therefore I have
come to the conclusion, which is supported by what is said elsewhere (Whitman,
pp- 21, 25), that the author means to designate only the clear central areas of the
radial systems as nuclear structures.
MUSEUM OF COMPARATIVE ZOOLOGY. 507
undoubtedly arises directly from the elements of the nuclear plate, and
therefore unquestionably corresponds with the “minute corpuscles” in
Nephelis, which have a like origin. Furthermore, the behavior of these
structures in both snail and worm at the time the first cleavage spindle
is forming, as already noted, is significant of their identity. But if they
are in reality the same, then some of the arguments advanced by Whit-
man will lose in significance when applied to Limax. Size certainly
cannot be claimed to indicate their nucleolar nature in Limax, nor will
it be at all satisfactory to attribute their great dimensions to the
action of such reagents as Biitschli used (acetic acid), since osmic acid
confirms the substantial accuracy of the observations in this respect.
It remains, however, none the less interesting and important to ascer-
tain the cause of the excessive minuteness which these bodies continue to
exhibit in Clepsine. I am inclined to think that a causal connection
may ultimately be discovered between the diminutive size of these
bodies and the segregation of a part of the nuclear substance to form
the remarkable polar rings, which, I believe, are not as yet known to
exist in other eggs. It is noticeable that the polar globules share this
diminutive condition with the corpuscles in question.
The objections to Biitschli’s studies, raised on the strength of Hert-
wig’s observation that acetic acid does not afford so reliable results as
does osmic acid, are in part valid, as an examination of the figures I
have given of Limax will show; but a veritable membrane will hardly
be claimed as a necessary part of a nucleus, any more than of a nucleo-
lus. Further, the use of chromic and osmic acids clearly shows in the
ease of Limax (Figs. 52, 68, 70, 72) that these bodies are not perfectly
homogeneous, but contain conspicuous structures, not at all to be con-
founded with vacuoles, and the reticulum which is characteristic of nu-
clei. The evidence of the acetic-acid specimens is in this point, then,
substantially corroborated by the use of other reagents.
The testimony of most recent observers as regards the growth of
these bodies at the expense of the surrounding clear substance (central
area) is so uniformly the same, that it does not seem necessary to dwell
upon this point. It appears to me that an even,greater obstacle to
Whitman’s interpretation is afforded by the male pronucleus of Limax,
which grows in size at the expense of the surrounding protoplasm with-
out the intermediation of any radial system or central area. One is
compelled to ask, If the body in question is a male pronucleolus, what
evidence have we in Limax of the existence of a male pronucleus? Yet
this structure is so entirely similar to what I have called the female
508 BULLETIN OF THE
pronucleus that their morphological equivalency cannot for a moment
be doubted. For Clepsine, however, Whitman speaks with the greatest
positiveness that “the central area does not disappear, nor even dimin-
ish in size,” though it is granted that the corpuscles increase a little in
their dimensions.
The chemical behavior of these corpuscles, even in the case of Clep-
sine, does not appear to me to be inconsistent with their nuclear nature ;
at least, that they are “ more deeply colored than the nucleoplasm” is
entirely consistent with an interpretation which makes of the “ nucleo-
plasm” yolk-protoplasm, and of the corpuscles, nuclei, since, as is known,
nuclei stain more vigorously than the surrounding protoplasm of the yolk.
The destiny of these bodies is to coalesce and then to participate in
the formation of the spindle. But their smallness in Clepsine seems to
preclude the idea of the spindle being formed exclusively, or even
largely, at their expense, whereas the size and elongation of the “ nu-
cleoplasmic”’ area is such as to produce a conviction that the spindle is
formed by the metamorphosis of the latter. Add to this the fact ob-
served by Whitman, that this nucleoplasm exhibits the same reaction
under treatment with osmic acid as the contents of the germinal vesi-
cle, and we have the strongest points that can be made in favor of
Whitman’s interpretation. I shall not attempt to deny that both
“central area” and spindle in Clepsine are largely due to a metamor-
phosis of this segregated plasm which Whitman calls “ nucleoplasm”;
on the contrary, I think we have good reason to believe that the same
is true, though to a less extent, in the case of Limax (compare Fig. 85) ;
that is to say, that in Limax also the two central areas arise outside of
(though not necessarily quite independently of) the two unfised bodies
which Whitman calls pronucleoli, and that they and the spindle owe
their origin in part to protoplasm which lies quite beyond the limit of
those two bodies. The only essential difference in the two cases will be
this: that, while in Limax all the nuclear substance (nucleoplasm) is
ultimately segregated to form a large nuclear structure, in Clepsine the
other events of the metamorphosis overtake, as it were, this segregating
process while enough nuclear substance still remains diffused in the
neighboring protoplasm of the yolk to give the observed reactions under
the influence of osmic acid.* But admitting the possibility of the exist-
* J wish to emphasize at this point the observation previously quoted from Whit-
man, — that ‘‘the nucleoplasm is more strongly colored in the centre, around the pro-
nucleolar bodies, than at the edges,” — for, in my opinion, this is evidence that his
so-called nucleus is not uniformly nuclear substance (nucleoplasm), but only proto-
ne —_—s
ee
MUSEUM OF COMPARATIVE ZOOLOGY. 509
ence of a potentially or prospectively nuclear substance outside the
corpuscles in question, does not involve the necessity of considering
such unsegregated substance to be a veritable nucleus.
However unsatisfactory this attempt to harmonize these two cases
may appear, I cannot hesitate to adopt it, if—as seems to ‘be the case
at present — the only other alternative is to hold the bodies under con-
sideration to be in the case of Limax pronucleoli.
O. Herrwie (’78*) has established in Mitrocoma the existence of a
vacuole much smaller than that which is derived from the inner half of
the second maturation spindle, and considers it to be the sperm nucleus,
even though no radial structure was discovered in the surrounding pro-
toplasm. He thinks this may be due to the difficulty of recognizing
such a radial structure when the protoplasm is homogeneous, as it is
here. From the evidence thus far gained in Limax it would seem that in
other cases it might not be possible to distinguish the stellate structure,
and that, too, where Hertwig’s explanation would be insufficient. These
two nuclear vacuoles, he continues, become mutually flattened, and in
the living egg suddenly cease to be visible, but in their place may be
found, after treatment with acetic acid, the customary spindle and
amphiaster.
In artificially fertilized eggs of Sagitta the yolk, before the first polar
globule is formed, withdraws somewhat from the vitelline membrane,
and a faint radiation may be detected at the vegetative pole. This
remains, as in the starfish, inconspicuous until the second polar globule
begins to be formed, when it increases in extent, and migrates toward
the centre of the yolk. It appears, says Hertwig, as though the plasma
when ruled by the process of division going on at the animal pole, could
not respond to the stimulus of the male nucleus in so liberal a manner
as later.
Interesting features of the conjugation of the two pronuclei in Sagitta
are, that as they approach each other they become pointed, and that
the pointed ends become applied to each other and assume a darker as-
pect (see Hertwig’s Taf. X. Fig. 18), as though the more compact ele-
ments were collected there, and the more fluid had receded to the
opposite ends of the pronuclei.. As far as relates to the altered form
plasm, in which the amount of infused nuclear substance at any given point is pro-
portional to its nearness to the central corpuscle. The gradual transition in the
nature of this ‘‘ nucleoplasm ” till it is no longer distinguishable from the surround-
ing yolk protoplasm, appears to me an important objection to considering it the
nucleus.
510 BULLETIN OF THE
this is very similar to what I have observed on hardened eggs of Limax,
and since Hertwig’s observations were made on living eggs there can be
little doubt that the condition I have represented in Fig. 68 is entirely
conformable to that which existed before the eggs were hardened. The
figure which Hertwig gives represents these structures as being more
angular than those | have figured, and I have detected no appreciable
difference in density between the narrower and broader ends. On the
other hand, Hertwig has figured the outlines as of equal distinctness
throughout, even when the pronuclei are in close proximity to each
other. For Limax I must repeat that, while the outline of each pronu-
cleus is not interrupted or effaced, it is much less boldly expressed at and
near its more pointed extremity. I doubt if this indicates a difference in
the composition of the two extremities of the nucleus. May it not be
that the density of the surrounding protoplasm changes with its distance
from the central point of attraction, in such a manner that it more
closely approaches the refringency of the pronucleus at the smaller ex-
tremity of the latter than it does at its more obtuse end? Sagitta and
Limax afford the only cases, so far as I recall, where this peculiar shape
of the pronuclei has been observed.
Hertwig’s observations on the formation and copulation of the pronu-
clei in mollusks afford several interesting points of comparison with
Limax. Thus, in the case of Mytilus, he says that they melt together,
and then become indistinct. In a pteropod (Tiedemannia), soon after
the first appearance of the two pronuclei, there was seen emerging from
the male pronucleus, in the part of the yolk’ not obscured by yolk
eranules, a filament which followed when this pronucleus advanced to
meet the female pronucleus. Meantime the clear protoplasm increased
in extent about the animal pole of the egg, and thus was brought to view
suecessively more and more of the filament, which remained visible till
the time of the first segmentation. Hertwig interprets this as being
the filament of a spermatazoon, which penetrates at the vegetative pole,
and remains at first concealed by the yolk granules of that portion of
the egg. The head of the spermatazoén (i. e. the nucleus of the sper-
matic cell) gives rise to the sperm-vacuole, and the filament remains to
be dissolved in the yolk during and after the first segmentation. The
pronuclei in this case reach dimensions proportionate to the same
structures in Limax. By the time they have attained this relatively
great size, a large number of nucleoli have been formed (ausgeschieden)
in them.
The next change which overtakes the nuclei does not seem to be the
MUSEUM OF COMPARATIVE ZOOLOGY. 511
melting together which is so generally observed to ensue. Hertwig says
the nucleoli suffer disintegration into clusters of small granules, which
collect on both sides of the conjugation surface ; then two dull stellar
systems make their appearance at two diametrically opposite points in
this plane of contact ; next, the contour of the two vacuoles suddenly
disappears, the nuclear fluid apparently mingling with the surrounding
protoplasm.
This agrees with what I have shown to take place in Limax, so far as
concerns the origin of the amphiaster of the first cleavage sphere before
the actual fusion of the pronuclei. Hertwig does not seem to have
observed any want of synchronism in the appearance of the two asters,
and moreover clearly places them on the boundary of the nucleus and
the protoplasm, just as Fol and many others have done. Without giv-
ing particular prominence to the fact, Hertwig makes the disintegra-
tion of the pronuncleoli precede the appearance of the asters. That I
consider to be a point of cardinal importance, and one which, in view
of the contrary results I have obtained, and in view of the fact that
Hertwig may not have observed the very first indications of an exist-
ing aster, should hereafter demand especial attention. Where do the
first signs of the approaching segmentation make their appearance, —
in the nucleus, in the yolk, or at the boundary of the two? The
definite answer to this question will, I believe, advance us a step in the
appreciation of the mutual relations of nucleus and protoplasm.
According to Hertwig, these changes occur in both Phyllirrhoé and
Pterotrachea in the same manner as in the pteropods, save that in the
latter genus the pronuclei secrete each only a single nucleolus. When
their contours disappear, the pronuclei contain, in his opinion, only
nuclear fluid (Kernsaft).
BuancwarD (78, pp. 754 — 758) summarizes the results of the recent
studies on fecundation which he has reviewed, and expresses his belief
that the homogeneous clear mass, at the expense of which the male pro-
nucleus grows, is not vitelline protoplasm, but rather that part of the
germinative vesicle which is dissolved in the vitellus at the moment
when the directive (first maturation) spindle is formed. He admits that
there is no direct evidence to prove this hypothesis: it simply seems to
him more rational than the other supposition.
512 BULLETIN OF THE
C. THEORETICAL CONSIDERATIONS AND GENERAL
CONCLUSIONS.
PRoMORPHOLOGY oF THE Ovum. — In the earlier stages of its growth
from an indifferent cell, the ovum remains for a time in the condition
of an homaxial body.* The polyhedral form, which so often obtains,
is not of fundamental significance; it is simply the temporal phase,
which its surroundings mechanically impose upon the ovum. This is
clearly shown by the spherical form which such ova usually assume as
soon as they are set free. The homaxial condition of the ovum is
evinced by the central position of its nucleus, the germinative vesicle,
as well as by the form of the protoplasm which constitutes its principal
bulk. Whether granular or more homogeneous, the latter exhibits in
every radius the same conditions.
Ultimately, however, one of its axes undergoes important changes,
and thus becomes differentiated from the remaining axes; these still
continue in a state of mutual equality. Such may be called the monaz-
ial condition, Although the differentiation of this axis is manifest in a-
variety of ways, and perhaps occurs at different stages of development
in different animals, there are still many reasons for believing that this
differentiated axis is homologous throughout the Metazoa. It may properly
be called the primitive axis. It is that —to mention a single one of
its characteristics — in which the maturation spindle lies just prior to
the formation of the polar globule. While the spindle may possibly fur-
nish in some cases the first readily appreciable indication of such a con-
dition, it is probably only one of the evidences of a pre-existing monaxial
state.
Since the differentiation of the primitive axis usually appears to be
coupled with a specialization of one of its poles, it remains at present
doubtful if a haplopolar monaxial stage intervenes between the homaxial
and the diplopolar monaxial conditions. I have, however, already (p. 186)
called attention to a condition of the egg in the development of Limax
which seems to realize the requirements of such a stage. The poles of
* Even in those cases (Vertebrata) where the permanent ova are formed by a con-
fluence of several primitive ova, the homaxial condition appears to be only tempora-
rily obscured, and is none the less an essential phase in the growth of the permanent
ovum. See Goette "75 and Balfour ’78°.
MUSEUM OF COMPARATIVE ZOOLOGY. 513
the primitive axis are often so unlike, that the differences are con-
spicuous to the naked eye, and have therefore been long known, — as in
the eggs of many batrachians, where one pole is pigmented, the other
less or not at all. The relation of the poles to subsequent stages of de-
velopment has also, in some cases, been long recognized. Hence have
arisen for them the numerous designations animal and vegetative, active
and passive, formative and nutritive.
There are objections to the employment of most of the names that
have been used. Thus, while active is an eminently fitting expression for
the pole where phenomena in such variety are exhibited, the opposite
pole cannot with as much propriety be said to be passzve, since it is in
many cases the seat of peculiar, although thus far unexplained activi-
ties. Formative and nutritive are doubtless preferable to the older terms
animal and vegetative ; but to speak of that pole which embraces the
peripheral aster of the archiamphiaster as formative is to attribute to
its substance a function which is confessedly inapplicable to a considera-
ble portion of it, viz. to the substance of the polar cells, which univer-
sally take no part in the formation of the embryo. It seems to me,
therefore, that the substitution of less contradictory expressions is de-
sirable. I would suggest the use of primary and secondary,* as being
entirely consistent with our present knowledge. The active pole is cer-
tainly first in importance, and it probably is the first to be raised from an
indifferent condition. The nutritive pole is consequently of secondary
importance, as in point of time its phenomena succeed corresponding
conditions of the primary pole.T
With the elevation produced by the first maturation spindle, at the
very latest, the form of the egg evinces its monaxial condition, and the
primary pole is prominently specialized. The secondary, on the con-
trary, usually remains undifferentiated ; a few cases, however, have been
observed in which it is characterized by changes of form or structure.
Probably the most remarkable is that of Clepsine, so carefully studied
by Whitman; but other instances of a peculiar modification of the
secondary pole have been seen, especially in the mollusks, and with in-
* The corresponding radii may also be similarly designated primary radius and
secondary radius. :
t Whitman ("78%, p. 20), for example, says of Clepsine: ‘‘ A short period of unipo-
lar activity is succeeded by a long period of bipolar activity which extends through the
cleavage stages. In the latter period the contrast between the two poles is still main-
tained; for the pole thus far active still asserts its pre-eminence by taking the lead in
actions that repeat themselves later and more sluggishly on the opposite pole. It is as
af one pole was trying to mimic the performances of the other.”
VOL. VI.— No. 12. 33
é
514 BULLETIN OF THE
creased attention it is altogether likely much additional information on
this subject may be gained.*
PoLtaR PHENOMENA. — Hatschek (77%, pp. 524, 525) seems to have
been the first to attach a general importance to evidences of polar differ-
entiation in early stages of development. It is probable, he says, that a
differentiation exists already in the egg cells of all Metazoa. It is most
conspicuous in eggs rich in nutritive material, and less evident in small
egos having little nutritive yolk.
Balfour (’75%, p. 210) had previously called attention to the signifi-
cance of a polar concentration of the nutritive portion of the egg in the
process of segmentation. ‘In none of these (vertebrate) yolk-containing
ova is the food material distributed uniformly. It is always concen-
trated much more at one pole than at the other, and the pole at which
it is most concentrated may be conveniently called the lower pole of the
ege. In eggs in which the distribution of food material is not uniform,
segmentation does not take place with equal rapidity through all parts
of the egg, but its rapidity is, roughly speaking, inversely proportional
to the quantity of food material.”
It is possible that this accumulation of nutritive substance is not
only an expression of the polarity so generally observable, but is also,
as it were, a mechanical cause of the condition, since the polarity is de-
termined during, and by the method of, the egg’s growth. In many
cases, at least, — as, for example, in Anodonta, — the acquisition of the
food yolk is a one-sided process. It is evident from Flemming’s work
(75, pp. 93, 94) that in the case referred to the animal pole is the one
which is less charged with nutriment, and perhaps this is because it is
more remote from the channel (micropyle) along which commissarial
activity is maintained.
The influence of the nutritive substance upon segmentation and later
stages in development was amply comprehended by Haeckel (’74, p. 159,
"74", p. 21) at a still earlier period, and has been utilized in his masterly
way to explain the superimposed modifications in the process of gastru-
lation.f Serviceable as its comprehension has proved in this latter
* Compare Lovén (48%, Pl. X. Fig. 8), Rabl (76, p. 316, Taf. X. Fig. 4), Hat-
schek (77%, pp. 504, 505, Taf. XXVIII. Fig. 1), and O. Hertwig ("78%, pp. 202,
209, Tal, x. Bio 5," Vat. XI. Fig;4).
+ ‘*Unter den secundiren coenogenetischen Erscheintngen aber, welche den pri-
miren palingenetischen Entwickelungsgang der Keimformen verdecken und falschen,
sind wieder vor Allen wichtig die Einflussreichen Verhaltnisse des Nahrungsdotters
im Gegensatz zum Bildungsdotter.” — Haeckel "75, p. 404. See also pp. 416-419.
MUSEUM OF COMPARATIVE ZOOLOGY. 515
direction, it is doubtful if the localization of the food material is compe-
tent to explain all the polar phenomena of the egg. In early stages
these may find expression in a variety of manifestations. The migra-
tion of the germinative vesicle toward a definite point in the surface ; the
radial position assumed by the maturation spindles; the waves of con-
striction which precede the formation of the polar globules, and the in-
equality in the sizes of the latter; the union of the pronuclei at a point
nearer the primary than the secondary pole and the consequently (?) ec-
centric position of the first segmentation spindle ; the appearance ‘of the
first segmentation furrow earlier at the primary than at the opposite
pole ; the formation of pseudopodia-like elevations, — often most con-
spicuous at the primary pole; the accumulation of finely granular pro-
toplasm at the secondary pole after the elimination of the polar globules ;
and the appearance of “ polar rings” and “ring rays” (Clepsine) at both
ends of the primitive axis, — are all indications of a polar differentiation
of the egg. The eccentric position of the germinative vesicle might in
many cases be induced by a regulated distribution of nutritive sub-
stance, and the point at which the polar cells appear might be predeter-
mined by the relation of the egg to its sources of nutrient supply ; the
direction of the wavelike constrictions, the region of greatest pseudo-
podal activity, and even the position of the spindle axis, might also be
dependent on the same (nutritive) conditions. But it must be in oppo-
sition to the obstructive properties of the nutritive substance, that the
elevation of protuberances at the secondary pole, the formation of the
aboral “‘ polar ring,” etc., take place.
A differentiation in the substance of the egg at a period preceding the
accumulation of deutoplasm, and regulating its distribution, must proba-
bly be assumed, and to this are to be referred the polar phenomena
which appear later. What may be the immediate cause of this hypo-
thetical earlier differentiation remains to be discovered. It is possible
that the topographical relation of the egg (when still in an indifferent
state) to the remaining cells of the maternal tissue from which it is differ-
entiated has an important influence in determining this axial condition.
It would certainly be interesting to know if that phase of polar differen-
tiation which is manifest in the position of the nutritive substance, and
of the germinative vesicle, bears a constant relation to the free surface
of the epithelium from which the egg takes its origin. If, in cases
where the egg is directly developed from epithelial cells, this relation-
ship were demonstrable, it would be fair to infer the existence of corre-
Sponding, though obscured relations, in those modified cases where (as,
516 BULLETIN OF THE
for example, in mammals) the origin of the ovum is less directly trace-
able to an epithelial surface. Although there are not many existing
observations which are sufficiently connected to allow a definite conclu-
sion to be drawn from them in this particular,* there are evidences
which in many cases point strongly to the existence of the relationship
suggested.
One of the results of a polar differentiation of the primitive axis is
often a difference in the specific gravity of the hemispheres, but it has
not been found that the conditions are the same in different animals.
Thus the primary pole is lighter in the eggs of frogs and the fowl, and it
has recently been shown to be the same in certain fresh-water pulmo-
nates (Rabl 75, p. 223), in Unio (Rabl 76), and in Clepsine (Whitman
"78%, p. 29); while in a Gadoid studied by Haeckel (75, p. 436) it was
found to be heavier than the secondary pole, thus causing the more
active hemisphere to be directed downward during the early stages of
development. In the study of fish eggs, probably nearly related to
those seen by Haeckel, Ed. van Beneden (’78, p. 43) observed a slightly
modified exemplification of the same thing.
The activities of the primary pole are partly of a more constant nature
and widely disseminated, partly either less regular and unlike in different
animals, or perhaps entirely absent. To the former belong the production
of polar globules, which will be considered later. Of the less constant
phenomena, perhaps that which has been most often described is the
pseudopodia-like elevation of portions of the cell protoplasm. This,
however, may be only a special manifestation of a more general amceboid
activity, not always resulting in the formation of pseudopodia, but
usually causing the concentration of the active portions of the egg at
special epochs in its development. Such concentrations are especially
conspicuous in cases where there is an early and sharply expressed
separation of the formative from the nutritive constituents of the
yolk. This has been observed, for example, in the Ctenophor just
before segmentation by A. Agassiz, Kowalevsky, and others; in osse-
* A manifest obstacle is encountered in the difficulty of determining after its de-
tachment the position which the egg held during its growth. Unless the germina-
tive vesicle is prominently eccentric both before and after the liberation of the ovum,
or the deutoplasm is conspicuously segregated before maturity, or the envelopes of
the egg present some differentiation (as, for example, a micropyle) which can serve as
a constant point of reference, it may be impossible to reach a satisfactory conclusion.
Observations of an axial differentiation in liberated eggs are sufficiently numerous,
but the orientation of the differentiated axis in the ovarian egg has rarely attracted
the attention of observers.
MUSEUM OF COMPARATIVE ZOOLOGY. 517
ous fishes before fecundation by Reichert, Oellacher, Van Bambeke ("76%,
pp. 1-12), and many others. In the less conspicuous form of a
gradual migration, it may be as nearly universal as the occurrence of
polar globules. Even in Limax, where no evidences of irregular pseu-
dopodal projections have been seen,* the primary pole becomes clearer
after the formation of the maturation spindle, and with the third act
of cleavage the antithesis between the two hemispheres reaches a
maximum. :
Whitman has concluded, from the position of the nuclear structure
near the primary pole, that the pseudopodal phenomena in Hydra, as
well as the “ Faltenkranz” of amphibian eggs, which he considers due
to the same cause, are to be classed with the radial arrangements of the
yolk during cleavage, and consequently to be referred to nuclear influ-
ence ; just as the place where the segmentation furrow is first to appear
depends on the location of the amphiaster, being always manifest earlier
on the side of the yolk toward which the segmentation aster is most nearly
approximated. As regards cleavage, I believe he is right in saying that
the same relation is probably true in all cases, —at least, I have met
with only two or three instances which seem to conflict with that rule.
I also agree with him in believing the phenomena have a causal relation.
He thinks the pseudopodia are most pronounced, and the cleavage first
expressed, at the primary pole, because of nuclear influence. But he
does not explain why the nucleus has this eccentric position, — why it
is near this pole rather than some other point of the periphery. The
nucleus appears ultimately to assume a position of equilibrium, not with
regard to the whole mass of the egg, but in respect to its active con-
stituents. Is not, then, this peculiarity ultimately, though indirectly,
* P. S. —The later observation reported on p. 180, foot-note, serves to show the
inconstancy of the pseudopodal phenomena. I believe they can be considered only
as special manifestations, whereas the polar concentration of active substance is ot
more fundamental significance.
t Kowalevsky (’75, Taf. XX XVIII. Fig. 14) represents a stage in the segmenta-
tion of Pyrosoma where the furrow seems to advance first from the side opposite that
occupied by the nuclear figure.
To judge from the figure given by L. Agassiz (’62, Pl. XXXI. Figs. 2, 3°), one
_ might expect to find the first cleavage furrow in Laomedea amphora appearing earlier
on the side opposite the peduncle, since in Fig. 2 the germinative vesicle lies nearest
that side of the egg. The natural though not necessary inference is that this side
corresponds to the primary pole. But it is stated (p. 313) that ‘‘the process of seg-
mentation... . commences by forming a furrow across the yolk on that side which
lies next to the peduncle of the medusa.”
See also the account (p. 419) of Giard’s statement for Salmacina.
518 BULLETIN OF THE
referable to the want of a uniform distribution of deutoplasm, — to the
polar concentration of the protoplasm, in other words ?
If the pseudopodia are attributable to the same influence as that which
produces the stellate figures of the yolk, they may not of necessity be
the direct result of nuclear influence. But of this I shall speak more at
length when considering the nature of asters. In Hydra, they are
manifest during the first and second cleavage, — less prominently after-
wards. In osseous fishes, according to Oellacher and Van Bambeke, they
occur before fecundation.* Kupffer and Benecke have described for
Petromyzon, beside more regular changes in the form of the primary
pole, a protrusion of clear protoplasm, which may be comparable with
the pseudopodia seen in other animals. According to these observers, it
is both connected with the elimination of the second polar globule, and
supplements the act of fecundation. Many observations, especially on
the Porifera by Haeckel and Schulze, tend to show the active amceboid
condition of the growing ovum ; but in these cases the differentiation
of the primitive axis appears to take place comparatively late, so that
a direct comparison with later and more specialized manifestations is not
permitted.
The entirely unique phenomena of “ polar rings” (see Whitman, "78*)
are in so far worthy to be classed here as they are special accumula-
tions of active protoplasmic (nuclear ?) substance, which manifest them-
selves soon after the formation of the polar globules. The “ring rays,”
which stretch out from them toward the equator at the surface of the
yolk like the pseudopodal filaments of many rhizopods, and the final
migration of their substance inward toward the segmentation amphias-
ter, afford ample evidence of the active nature of their substance. But
how the dispersion of this substance in “ring rays ” can be due to nuclear
attraction is not clear.
The changes which have been observed at the secondary pole are not
numerous. The most interesting is that of the “aboral ring” and its
rays in Clepsine. The others are limited, so far as I know, to the
elevation of masses of active protoplasm, and their appearance is as
unaccountable as that of the aboral polar ring.
By the figures which O. Hertwig has given of this phenomenon in
Mytilus, one is reminded of the description which Bobretzky (’76, p. 102)
has given of the early stages of segmentation in Nassa; and it may per-
haps be of significance in the study of these polar phenomena, that there
* P. S. — As has been stated (p. 180), they may occur in species of Limax during
the formation of the polar globules.
MUSEUM OF COMPARATIVE ZOOLOGY. 519
is in this case a complete separation and subsequently a confluence of the
vegetative blastomere with one of' the smaller cells at the animal pole.
The equatorial zone of clear protoplasm occasionally seen in the eggs
of Limax (see p. 183) is possibly another phase of the protoplasmic activ-
ity which is usually manifest about the poles of the primitive axis. But
all these phenomena have been too little observed to afford grounds for
deciding on the nature of the forces which produce them.
Asters. — Stellate figures make their appearance in connection with
two processes, — cell division, and the formation of the male pronucleus.*
* The aster which accompanies the origin of the female pronucleus is one of the
asters of a cell division. It is possible that this aster is entitled to a separate desig-
nation, —female aster. The accounts given by Fol (’77°, pp. 450, 451) and O. Hert-
wig (78, p. 166) for the starfish are not in complete agreement. Fol says of the aster
which remains in the yolk after the elimination of the second polar globule, ‘‘I] ne
tarde guére a s’effacer et 4 se changer en une ou deux petites taches,” etc., and subse-
quently he says, “‘ Les stries radiaires, peu accentuées du reste, que l’on remarque au-
tour du pronucléus en voie de croissance s’effacent et lovule entre maintenant dans
une nouvelle période dinactivité.” Although he does not say definitely that there is
no connection between these two stars, I think it is fair to assume that to be his be-
lief, for he gives a figure of an intermediate stage (Fig. 12) in which no rays are rep-
resented. Hertwig, on the contrary, does not figure any stage in the early growth of
the female pronucleus which is destitute of rays. In the text he says that a quarter
of an hour after the formation of the second polar globule the homogeneous place ex-
isting in the egg, [the ‘‘area” of] the internal half of the amphiaster, has increased
in size and retired somewhat from the surface. A number of sinall vacuoles arise in
this:homogeneous substance. In its vicinity the protoplasm toward the centre of the
egg has assumed a radial condition. The vacuoles increase in size, the radiation in
their vicinity becomes more distinct, and stretches out farther into neighboring parts.
During the confluence of the vacuoles, and the migration of the resulting Eikern
toward the centre of the yolk, the rays become less distinct and finally disappear. I
find in his account no ground for supposing that the rays about the female pronucleus
have an origin distinct from the deep aster. The nucleus, it is true, is represented by
both authors as occupying the centre of the radiation. That certainly is not the rela-
tion in ordinary cell division, and in so far a distinction is justified. The fact that this
radiation as described by Hertwig increases during the migration of the pronucleus and
then diminishes, also seems to warrant one in ascribing to it a significance different from
that prevailing in ordinary cell division. In Limax I find nothing to support Fol’s view
of the separate origin of a female aster. The internal aster of the second archiamphi-
aster increases in extent toward the end of the formation of the second polar cell, and
possibly after its detachment also; but whether this warrants a fundamental distinc-
tion from the asters of ordinary cell division seems very doubtful. There is little in
the conditions shown by Limax to support any argument drawn from the concentric
position of nucleus and aster (compare Figs. 57-60, 68, 72). Most of the investiga-
tions on other animals afford even less evidence than the starfish of the separate nature
520 BULLETIN OF THE
These two asters are, however, in so many points alike, that one is war-
ranted in considering them, for the present at least, as the results of like
processes. The relation which the centre of the aster sustains to the
growing nucleus in cell division cannot be urged as the basis of even a
topographical difference, for Fol has recently reported a condition in the
case of the male pronucleus of Sagitta, which shows conclusively that the
centre of the male aster does not necessarily coincide with the centre of
its nuclear structure, any more than new nuclei are coincident with astral
centres in division.
The most detailed, and, so far as one can judge without personal ob-
servation of the same object, the most accurate description of the changes
introducing the nuclear metamorphosis is that given by O. Hertwig for
the germinative vesicle of Asteracanthion. The first changes are ob-
served in the protoplasm which surrounds the vesicle. The protuberance
of protoplasm which invades the vesicle has a clear spot near its apex
free from granules, and it sends out long protoplasmic ridges which en-
croach upon the vesicle. Although he intimates that the first small aster
of the female aster. There is, however, another instance, Sagitta, in which the fe-
male pronucleus is represented as occupying the centre of an extensive radial system
(O. Hertwig, "78%, Taf. X. Fig. 11). Fol, however, makes no mention of such a sys-
tem, which seems the more remarkable as he observed the peculiar condition of the
male aster in Sagitta.
Another radial figure, that which surrounds uniformly the conjugated pronuclei,
may also possibly be a separate phase of the astral phenomenon. For the present,
however, I believe it may safely be regarded as a continuation, and perhaps an exten-
sion of the so-called male aster. O. Hertwig ("75) has described it in Toxopneustes
(pp. 400, 401) as though it might be genetically connected with the two asters which
arise at the first segmentation, as well as with the male aster, but in his general con-
clusions (p. 416) he has very definitely stated that this old single nucleus is dissolved,
and that the asters of segmentation arise as new structures. Hertwig and Selenka
agree in making the male pronucleus much smaller than the female when they come
in contact, and Selenka has recently come to the conclusion that the former continues
to increase in size until it equals the latter before there is a real fusion of their sub-
stances. May it not be that the extensive radial system surrounding welded but un-
fused pronuclei is only a male aster which ceases to exist when its nucleus has attained
normal dimensions? It is possible that the aster of the female pronucleus, when such
exists, shares in the production of this central sun. The entire absence of both male
and female asters in the case of Limax might perhaps in that event be a sufficient ex-
planation of the non-appearance of a conjugation aster ; but it cannot be denied that
the fusion of male and female pronuclei might also generate a force capable of induc-
ing similar radiations, for there is reason to believe that their substances are suffi-
ciently unlike to exert a mutual attraction.
But if either of these asters is constantly developed, it remains yet to discover the
means of making their rays visible.
MUSEUM OF COMPARATIVE ZOOLOGY. 521
arises subsequently in this protuberance, I cannot think these radial ridges
are due to anything different from that which causes the true asters.
The appearance of one or both the asters seems, then, to be the first
change in the approaching metamorphosis. That is entirely consonant
with the observations made on the nuclear metamorphosis preceding the
first cleavage in Limax. It is certainly a matter of no great importance
whether the invasion takes place a little earlier-or a little later in the
history of the formation of the asters. In Limax the asters are often so
far removed from the nucleus that they must attain considerable size
before any conspicuous changes are effected in the latter. In other cases,
as, for example, in the pteropods as shown by Fol, the earliest evidence
of the existence of a star is to be seen within the outline of the nucleus.
I do not conceive, however, that cases like the last really conflict with
the conclusions just stated. The transparency of the nucleus may be in
itself enough to explain the detection of rays through its substance sooner
than in the surrounding protoplasm. Fol’s ("77°) account of the meta-
morphosis of the germinative vesicle in Asterias glacialis seems to indi-
cate that the asters arise at a much later period, namely, after radical
changes have taken place in the germinative vesicle and in the germina-
tive dot. It is without doubt one of the most delicate and difficult of
the questions connected with maturation, to ascertain when and where
the first traces of the archiamphiaster appear. But unless this author’s
final paper brings strong evidence to show the inaccuracy of Hertwig’s
observations, it seems to me we may accept the latter as entirely trust-
worthy in this particular. Certainly the figures accompanying Fol’s pre-
liminary paper in no way invalidate the evidence given by Hertwig, for
in the earliest stage figured in which acids had been employed (Fig. 5)
not only are both asters formed, but the spindle is represented and also
its equatorial thickenings. But that condition represents a stage much
advanced beyond the first appearance of the first aster. The want of
evidence that asters exist in the stages represented by the figures which
precede may be due to their all having been made from living eggs. It
can scarcely be doubted, for example, that the stage shown in his Fig. 4
is more advanced than that exhibited in Fig. 5, since the oblique or tan-
gential direction of the spindle (Fig. 5) precedes rather than follows the
radial position (Fig. 4). Concerning the statement that the amphiaster
is formed within the germinative vesicle, or what remains of it, but is
from the beginning eccentric in position, I can only say that the drawing
(Fig. 5) is not sufficient to prove that the centres of the asters lie within
the finely granular territory which I take to be the remains of the ger-
522 BULLETIN OF THE
minative vesicle ; and even if it did show this, it would not follow that
such a position could not have been effected by the invasion of an aster-
bearing protuberance of vitelline protoplasm, in the manner described by
Hertwig.
There are no accounts by other authors in which the centre of the
aster is shown to lie within the nucleus, — none in which it is not pos-
sible to suppose that the protoplasm surrounding the nucleus takes at
least an equal share in the formation of the asters. From the cases given
above it will be sufficiently clear that the converse of this proposition
does not hold true. So far, then, as regards the origin of asters, I hold
that they are primarily phenomena of the protoplasm rather than of the
nucleus. Ido not wish, however, to deny to the nucleus the possibility
of any influence in their production, but must insist that the immediate
cause of their appearance is not of necessity a morphologically persistent
part of the nucleus.
The male aster appears to present the most serious obstacle to this
view of the origin of molecular stars. If it be granted that they are
essentially like other asters, it may pertinently be asked what evidence -
there is that the star is not due to the direct influence of the nuclear
substance (male pronucleus), toward the centre of which its rays are di-
rected. From my own observations on Limax | should hardly be able
to give any satisfactory reply ; the only asters which I should feel justi-
fied in referring to the influence of the male element are those which
occur in the single abnormal case described. The short rays are there
directed toward central corpuscles, which I have assumed to be equiva-
lent to the male pronuclei seen by other observers, so that the evidence,
little as it is, would be unfavorable to the view I have adopted. But
Fol’s (77°, p. 465) observation above alluded to may possibly offer an
explanation of the difficulty, and ultimately prove that the male aster
is, after all, only an apparent exception. Fol states that in Sagitta, dur-
ing the motion of the male pronucleus toward the female, it is very evi-
dent that the centre of the star (male aster) is in advance of the clear spot
(male pronucleus), and that the latter 1s drawn on in a passive manner,
The figures which O. Hertwig has given of the pronuclei and their asters
in Sagitta do not, it is true, directly confirm this observation, but the
pear-shaped outline of the pronuclei, when compared with similar forms
which are shown in Limax (Fig. 68) to be probably due to the attrac-
tion of an aster, is sufficient to suggest the possibility that this peculiar
contour in Sagitta has been produced by a like cause. Unfortunately,
Fol has not stated whether the pronucleus suffers any change of form as
MUSEUM OF COMPARATIVE ZOOLOGY. 523
a result of the traction; but taking into account Hertwig’s figures and
what I have seen in Limax, I am inclined to think that all are due to
the same cause, and that the male aster centres, as Fol claims, in ad-
vance of the nucleus, and at least may induce its elongation. In that
event, the exact centre of radiation has not been clearly seen by Hertwig.
If so experienced an observer has overlooked the true relation of nucleus
and aster in so favorable a case as that of Sagitta, it will not be too much
to say that renewed observations directed especially to this point may
prove that the relation of aster to nucleus has hitherto been only par-
tially comprehended.
Whether, however, the formation of asters can really be regarded as
the first visible alteration in the nuclear metamorphosis, may still be
open to question. There are many descriptions of important changes
occurring in the nucleus prior to the detection of any stellate figure.
Especially in the metamorphosis of the germinative vesicle is this the
case. But, from one cause or another, most of these descriptions can-
not be considered as definitely excluding the possibility that stellar fig-
ures accompany or precede the indicated changes. The very careful
account of the metamorphosis of the germinative vesicle in Asteracan-
thion given by Van Beneden, for example, affords no means of deciding
this question, since he failed to discover the asters at any stage. The
necessity in most cases of using reagents to demonstrate the stellar rays,
makes all continuous observations on living specimens of little or no
value in endeavoring to ascertain the synchronism of the astral phenom-
ena and the changes within the nucleus. Were the first detection of
rays in déwing eggs equivalent to finding the very beginning of such
structures, the question would have been long ago definitely answered
by Auerbach’s studies, for he recorded the disappearance of the nucleoli
at the time of the confluence of the two pronuclei, and observed the
stellate figures only at a later period. But the timely use of reagents
would probably have shown the existence of asters at stages as early as
those in which they are found in Limax.
A possible objection to the view that stars introduce the nuclear meta-
morphosis is presented in the division of tissue cells, where astral figures
of the protoplasm are less pronounced or altogether invisible. Here the
relatively great size of the nucleus, and the prominence of its labyrinthine
filaments are such as to make a study of the radial appearances in the
cell protoplasm much more difficult and unsatisfactory than in early em-
bryonic cells. But even here, according to Flemming’s studies on the
epithelium of the salamander, centres of attraction are found at the poles
524 BULLETIN OF THE
of the nucleus during the first phase of the intranuclear changes.* Al-
though the plane of division is seldom inclined sufficiently to allow one
to look, even obliquely, on the pole of the prospective spindle, yet stel-
late arrangements of the scanty pigment granules and fat globules of
the protoplasm are to be seen. These Flemming compares, with justice,
to molecular asters. It follows from his observations, I think, that we
have as yet no grounds for presuming that the stellate figures in tissue
cells are dependent on preceding alterations of the nucleus, — certainly
not that they are brought about by a segregation or localization of nu-
clear substance. There is nothing in Flemming’s figure of this stage
(Taf. XVI. Fig. 2a), nor in the text, to indicate that there is at this time
any evidence of a dicentric arrangement on the part of the nuclear fila-_
ments themselves. In cases where, from tne absence of granules in the
protoplasm, these asters are not rendered visible, it is none the less prob-
able, as Flemming maintains, that they exist.
But there are cases in which the division of the nucleus is in all prob-
ability not accompanied by such fundamental rearrangements of its
substance as appear in the various modifications of the spindle figure. —
Thus far, I believe, no trace has been found of molecular asters in these
instances of direct nuclear division. That, however, does not warrant
the-conclusion that asters, being formed about a segregated portion of
the nucleus, are here wanting because no such localization of nuclear
substance has taken place. The only inference which seems to me justi-
fiable from this evidence is, that the filamentous and other differentia-
tions of the nucleus are correlated with the existence of molecular asters.
It affords no means of ascertaining the nature of this relationship, and
therefore is without significance in any attempt to answer that question.
As regards the evidence to be drawn from the so-called free nuclei, it
is too limited to be of great value. The view that these nuclei do not
arise de novo, but result from the division of previously existing nuclei,
has only recently been gaining support, and there are not many observa-
tions on their division. Whitman (78%, p. 272) has “seen these nuclei
(his entoplasts) pass through the successive forms of a dividing amphi-
aster,” and Balfour (’78, p. 17) has shown that his “‘ yolk nuclei” some-
times present much the same appearance of a double cone as do the
nuclei in the germinal disk. While the former observer certainly saw
the astral figures, the latter, it must be concluded, did not, for he gives
* ‘¢Wichtiger ist eine innere Verinderung im Zellenleibe: Schon in diesem Sta-
dium (1. Phase) existirt in ihm, wie ich kurz sagen will, eine dicentrische Anordnung,
den kiinftigen Theilungspolen der Kernfigur entsprechend.”— Flemming, 78, p. 372.
MUSEUM OF COMPARATIVE ZOOLOGY. 525
no representation of them in his figures, and says in the text (p. 24) that
these conelike nuclei of the yolk exert no influence on the surrounding
protoplasm. It is perhaps impossible to draw a conclusion of universal
applicability from these accounts, but it will be granted that it is pos-
sible for stellate figures to accompany the division of nuclei in syncytia,
as well as in definitely limited cells. The existence of asters in syncytia
once established, it still remains to be ascertained whether they will cast
any light on the supposed share which the nucleus takes in their pro-
duction, or on the nature of the influence they exert upon the nucleus
during its division. For the present I see no reason to anticipate the
«necessity of modifying the views I have arrived at from a study of cell
nuclei.
Plant cells rarely afford the opportunity of studying the radial phe-
nomena in the protoplasm during nuclear division, as Strasburger and
others have already pointed out. Why the centres of attraction exert
apparently so little influence on the protoplasm, it is difficult to say.
The great size of the nucleus as compared with the mass of the cell pro-
toplasm, and the vacuolation of the latter, are features which restrict
the possibility of well-marked asters. Certain it is that they are not so
clearly defined as in animal cells, though there are evidences of a radial
tendency in the protoplasmic filaments of Spirogyra, etc. The poles of
the spindle are usually so near the surface of the protoplasm that there
is little opportunity to form extensive rays. Cases where the centres of
attraction lie wholly outside the nuclear structure in plants (Isoétes) are
not numerous, but I cannot think such unfavorable objects as plant cells
and animal tissue-cells are competent to cast doubt on the nature of what
is so evident in the segmentation of eggs. Strasburger gives assurance
that in division the nucleus first becomes homogeneous, and then a con-
trast is developed between two opposing points of its surface. The latter
are doubtless equivalent to the astral centres, and the difference in the
order of events as compared with Limax may possibly be explained as
resulting from the inconspicuous nature of the asters in plant cells,
whereby their earliest stages have been overlooked.
In what precedes I have endeavored to show the possibility of a much
earlier origin for the asters than has generally been recognized, — that
they precede the disintegration of the nucleus, and are therefore to be
looked upon, not as the result of a segregation already effected in the
nuclear substance, but as the seat of forces actively engaged in remod-
elling the constituents of this central body. So long as it remained
undisputed that the centres of the asters lay within the nucleus, or at
526 BULLETIN OF THE
its boundary, no valid objection could be raised to considering them
(the centres) as localized portions of the nuclear substance, — the less
objection since their deportment under the action of staining fluids was
such as is exhibited by nuclear substance. Now the case appears some-
what changed. The fact that they may lie at some distance from the
nucleus while the membrane of the latter is still intact, seems to preclude
the possibility of any formal elements of the nucleus taking part in their
initiation. It does not, however, prevent the supposition that fluid por-
tions of the nucleus may have traversed its membrane, and have been
recondensed, so to speak, in the form of “areal corpuscles.” Still these
corpuscles, when they exist, do not stain as deeply as the nuclear disks, -
and are possibly only condensed portions of protoplasm. The nature of
their staining, however, indicates that they probably are composed ex-
clusively of neither nuclear substance nor cell protoplasm, but are pro-
duced by a fusion of the latter with fluid constituents of the nucleus.
The position of the centres of attraction constantly in the vicinity of the
nucleus, rather than in remote parts of the cell, is indirect evidence that.
the nucleus exercises some influence in their production. But one is
incapable of saying why the asters appear at particular points, and why
there are just two of them. That they do not appear at the same instant
is evidence that they are to a certain extent independent of each other.
The regularity with which they arise in positions definitely related to’
the main axis of the egg at the first division, and to the plane of the last
preceding division in subsequent stages, shows clearly that their location
is controlled in accordance with fixed laws, and it may be reasonably
conjectured that the distribution of the active protoplasm (or, what
amounts to the same thing, the position of the nutritive portion of the
yolk) is an important factor in determining the law. Yet it is not the
only factor ; since in the first division of Limax, for instance, it might
determine in what one of an infinite number of latitudinal planes the
asters should lie, but it probably could not influence the selection of any
one of the infinite number of diameters in that plane for the astral pair.
The latter might possibly be effected by the direction from which the
male aster approaches the female, and thus its determination be ulti-
mately referred to an entirely fortuitous circumstance, —the location of
the point where. the spermatozoén effects an entrance into the yolk.
This, however, I doubt, since I have not been able to conclude that the
asters have any fixed position in relation to the two pronuclei or their
plane of contact. If, as Fig. 79 seems to show, one of the asters could
make its appearance before the contact of the pronuclei, it is difficult to
MUSEUM OF COMPARATIVE ZOOLOGY. 527
conceive what influence the mutual relation of the pronuclei could have |
in determining the place of the two stars. From my observations on
Limax I am of the opinion that the pronuclei exercise only a limited in-
fluence on the position of the first amphiaster. As the centres of its
stars may lie deeper in the yolk” (farther from the animal pole) than the
pronuclei, I am induced to. think that their positions are determined
by some unknown influence which probably resides in the protoplasm
itself, and in this I see another reason for hesitating to consider the
asters as the result of an attraction exerted by a part of the nuclear
body on surrounding protoplasm.
The theory that the stellate figures are due to the outstreaming of
nuclear fluid from the nucleus undergoing division or disintegration,
leaves the existence of male asters without an explanation, for there is
no pre-existing accumulation of nuclear fluid to be thus put in motion.
Even as applied to the nucleus undergoing division, it is confronted by
serious obstacles, some of which I have already (p. 286) stated. As with
every other theory which involves a circulation of fluid, the results ap-
pear disproportionate to the protracted period during which the supposed
“flow” is maintained. There is no accumulation of the clear (nuclear?)
fluid at the peripheral ends of the rays such as might be expected to re-
sult from so long continued a current, and when the rays ultimately dis-
appear it is first at their peripheral ends, — not at their central ends, as
would naturally result if there were an outflowing stream. Apparently
the only way. of explaining this method of disappearance, in keeping with
the theory of centrifugal currents, is by assuming that the nuclear fluid
in the rays becomes diffused through the yolk, and that this diffusion
begins, or proceeds more rapidly, at the distal ends of the rays, thus
inducing their earlier obliteration near the periphery. But, if that were
possible, might not the original distribution, as readily as this, have
taken place as a uniform diffusion through the whole yolk without en-
gendering any astral figure? Certainly the rapidity with which the stars
grow is not so much greater than that of their disappearance as to make
it possible for simple diffusion to accomplish one, and not the other. It
is also incredible that fluid forced from the tips of an elongate nucleus at
so slow a rate as must be conceded, should exhibit such fineness and
such marvellous uniformity in the nature and the direction of its cur-
rents, unless some pre-existing structural condition determined its
course.
But the principal objections to this view, which was first advocated by
* See Figs. 85-89,
528 BULLETIN OF THE
Auerbach, are the facts that the asters have been shown to arise at a dis-
tance from the nucleus, and before the latter had suffered recognizable dimi-
nution in volume.
The idea that the asters are the optical expression of currents of clear
protoplasm setting toward the “centres,” has much more in its favor
than the theory of centrifugal currents. It does not conflict with the
view, in support of which there is much evidence, that these are centres
of attraction, and it is readily harmonized with the fact that there is an
accumulation of clear substance — the “ areas ” — about these centres,
which seems to present the same properties as the substance of the rays.
It, nevertheless, appears insufficient to explain all the observed phe-
nomena. If the star is due solely to centripetal currents, it is unin-
telligible how it should attain such a size as it often does without
a corresponding accumulation of clear substance at the centre, or why,
on the other hand, “ les rayons de l’aster male ne commencement & se
montrer nettement que plusieurs minutes aprés la fecondation et lorsque
la tache claire s'est deja avancée un peu vers Il’intérieur du vitellus.”
(Fol.) Another obstacle to this view is the deportment of the rays
in certain special conditions of the aster. If the spiral course which
they sometimes exhibit is induced by any mechanical or other influence
after their formation,* it seems impossible to explain them as simply
currents of either protoplasm or nuclear fluid, since any extraneous
force which could produce such extensive alterations in the direction of
the rays would obliterate so susceptible a thing as a stream of fluid.
But whatever may be the conclusion respecting the rays of the spiral
asters, the lateral deflection of those constituting the peripheral star
during the formation of the polar globules is evidently the result of a
mechanical influence. They are secondarily altered in direction, but
maintain their individuality, notwithstanding the pressure which pre-
vents their assuming a rectilinear position. If in this case the rays
were only streams of fluid, the resistance offered by the egg envelope
would merely result in shortening them without causing any such modi-
fication of direction as has been repeatedly observed. The astral rays
are visible in virtue of their possessing different refractive power from
the intervening portions of the protoplasm, not simply by reason of the
* If it were assumed, on the other hand, that the spiral condition was not super-
induced, but was from the beginning of their formation characteristic of all asters in
which it is found, it would be difficult to explain why the currents followed such a
systematic and yet indirect course, unless one assumed in addition the pre-existence
of a special structural condition of the protoplasm determining the direction of the
currents. But there is nothing else to favor this latter assumption.
MUSEUM OF COMPARATIVE ZOOLOGY. 529
displacement of yolk granules. The assumed motion is, therefore, not
enough to account for the appearances ; it offers no explanation of this
difference of refraction. No satisfactory explanation of the cause of
the latter will necessarily exclude the possibility of a motion, but it
cannot rest on that assumption alone ; for however definite the course
of the flow, it could produce no such optical effect until there was a
differentiation into more refractive and less refractive portions.
If the aster is only the optical expression of currents in the proto-
plasm, it remains to be explained why it is that such currents do not
uniformly produce this effect. There certainly may be a flow of sub-
stance without astral figures. The male pronucleus in Limax, for exam-
ple, grows within a short time to a comparatively large size without
necessitating the existence of any astral phenomena, and yet it cannot
be doubted that it grows at the expense of the substances of the yolk.
There is no reason to suppose that it has greater power than the male
pronuclei of other animals in rendering assimilable the substance in its
immediate vicinity, and that it may therefore dispense with far-reaching
protoplasmic currents which are necessary for their growth. If there are
currents in the one case, there doubtless are in the other, and their
magnitude and velocity, if proportionate to the rapidity of nuclear
growth, will not be less in Limax than in the average of other cases.
On the other hand, asters may possibly remain for a time unaccom-
panied by corresponding movements of clear protoplasm ; at least, there
are often great differences in the size of the areas which form the cen-
tres of asters having nearly the same extent.*
It is not to be overlooked that the areas may not be exclusively due
to an accumulation of clear protoplasm, and thus to an indirect repul-
sion of the granules of the yolk. It has not yet been shown that it is
impossible for the granules to have been employed in the chemical
changes presumably taking place at the centre of the aster, — that is,
that their disappearance from the “area” may not be due as much to an
actual chemical alteration as to a mechanical dislodgment.
The subsequent occupancy of the region of the central area by granu-
lar protoplasm is an argument neither for nor against the physical dis-
placement of granules from the area. The clear substance is at least
largely consumed in the growth of the nucleus. As the latter does not
migrate far enough to have its centre occupy the place of that of the
aster, this consumption of areal substance necessarily implies its re-
* Compare Limax, Figs. 73 and 80°, with Fig. 85 ; also O. Hertwig, "75, Taf. XIII.
Figs. 21 and 23.
VOL. VI. — NO. 12. 34
530 BULLETIN OF THE
moval from the area, and this motion is compensated by a corresponding
(centripetal) movement of the granular protoplasm. The same, it is true,
could not be claimed for the clear rays, for their place is subsequently
occupied by granules which it is fair to presume were simply displaced
during the astral manifestation, since the granulation of the yolk is not
permanently diminished by their formation.
I do not claim that there is absolutely no transfer of substance to and
from the centres of attraction,— on the contrary, I believe the phenomena
are, on any other assumption, unintelligible; but it seems to me that
the formation of a clear area and the existence of radial striations are far
from commensurate, and that to claim that the rays are only the optical
expression of currents is to associate as cause and effect two things which
have not necessarily any such connection with each other.
The view suggested by Strasburger, that the rays are evidence of the
polarity of the protoplasmic molecules, seems to imply that the astral con-
dition is effected by the molecules having the direction of their principal
axes so altered as to be radial, — that is, practically parallel to each
other, — this position being maintained by the (attractive?) influence
emanating from the so-called centres. But the spiral asters (unless they
are Superimposed conditions) appear unexplainable upon this hypothesis,
since the direction of the force must always be strictly radial, and the
attracted molecules could assume all intermediate attitudes between the
radial and nearly tangential only by the intervention of other forces, of
the existence of which we have no other evidence. If the rays are due
to the polarity of the molecules, their position must be very unstable,
and it will exist only so long as the attractive force continues to be
exerted. In hardened specimens the force is of course interrupted, and
the astral conditions are preserved only in virtue of being fixed by the
reagent before the latter had interrupted the processes generating the
supposed force. The cntensity of the attraction (or repulsion) must of
necessity diminish with the distance ; but does that warrant the lapse of
such an interval as occurs between the time when the central mole-
cules respond to the force and that when those near the periphery give
evidence of a like condition? But, further, Ido not understand how
such an orientation of all the molecules could accomplish a difference
in the refractive properties of neighboring rays of the protoplasm. It
would not be claimed that the molecules are directly visible, or that
their alignment was capable of direct observation. The protoplasm
would still remain homogeneous.
Biitschli’s opinion, that the asters are he optical expression of a
MUSEUM OF COMPARATIVE ZOOLOGY. 531
physico-chemical alteration of the protoplasm emanating from the cen-
tral area, is probably incontrovertible; at least there is a physical
alteration of the protoplasm, and it first becomes apparent at the centre
of the aster; but this is rather a description than an explanation of the
appearances.
I have already dwelt upon some features of the astral phenomena
which seem to strengthen the position maintained by Flemming, — that
the asters represent a structural condition of the protoplasm; but that
simply implies a greater stability in the nature of the rays —a closer
approximation to a solid condition — than is generally maintained, and
offers not the least explanation of the cause.
The substance which composes the central portion of the asters ac-
companying division was uniformly described by the earlier observers as
an accumulation of homogeneous protoplasm, and as such it always ap-
pears in the ling egg. Flemming was the first to show that a portion
of this “central area” is differentiated as a corpuscle capable of a slight
degree of staining, and for that reason he took the corpuscle to be the
beginning of a new nucleus. O. Hertwig has also recognized in all his
studies the existence of a stainable corpuscle occupying the centre of the
area, and has reproduced it in nearly all his more recent figures with
almost diagrammatic uniformity as a very minute body in which the
spindle fibres terminate. Strasburger has represented nearly the same
condition in his revised studies of segmentation in animals. In the
opinion of both these observers, the centre of the aster is occupied by a
visible portion of the old nucleus. The evidence that this corpuscle is
nuclear substance they find in the constancy with which it is stained, as
well as the fact that it forms the tip of the old nucleus when the latter
is drawn out into the form of a spindle.
My own studies lead me to believe that different reagents are not uni-
form in their effects, and I would refer to this some of the various condi-
tions in which the corpuscle has been exhibited by the preparations in
the case of Limax. It is quite improbable that all the variations are
thus referable, but it cannot be doubted, I think, that certain acids are
much more likely than others to make visible a differentiated central
corpuscle. In acetic-acid preparations the whole area has generally ap-
peared nearly homogeneous and usually not well defined, but sometimes
(Figs. 22, 25) quite sharply limited and free from every trace of internal
structure ; in a few instances, as though composed of a flocculent mass
(Fig. 55). In certain stages of the archiamphiaster (Figs. 43, 48, 50)
it has been occupied by a large more or less flattened corpuscle, which
532 BULLETIN OF THE
was nearly as extensive as the whole “area”; and, finally, at an early
stage in the formation of the first segmentation amphiaster, by a few
scattered (Fig. 85), or more definitely grouped (Fig. 82), refringent cor-
puscles. Since these various conditions exist in eggs that were sub-
jected to nearly the same treatment, it is not possible to account for the
differences as due to the action of the acid. Still, the nearly homoge-
neous condition is the one by far the most prevalent with the employ-
ment of acetic acid.. With osmic acid, which according to Hertwig is
the most satisfactory to demonstrate the existence of nuclear substance,
I have not uniformly succeeded in showing a central body, but with
chromic acid a small, lustrous, sharply limited corpuscle is almost always
distinguishable (Figs. 44, 52) exactly in the centre of the radiation. A
comparison of Fig. 52 with Figs. 73, 79, and 80 will illustrate the dif-
ferences which result from treatment of the same stages with different
reagents. It may possibly appear significant of the accuracy of Hert-
wig’s view of the nature of this areal corpuscle, that it is already differ-
entiated at the earliest stages in the formation of the aster which I have
seen. I cannot deny, in those cases where the nucleus elongates and its _
poles are observed to occupy the centre of the aster, that the most natu-
ral inference is that the corpuscles are segregated portions of the nuclear
substance, but in the case of Limax the assumption seems impossible.
These areal corpuscles lie outside the sharply marked territory of the
nucleus, often at a considerable distance, and there is no evidence of a
direct connection between the two. From theoretical considerations it
may be difficult to explain the activities of the astral centres without
admitting a fusion of nuclear and vitelline substances, since it is not
plausible that a chemical process should be initiated in a homogeneous
substance without the presence of a second material differing in compo-
sition from the first ; but the mingling of vitelline and nuclear matter
does not necessitate the appearance of the latter in the form of discrete
corpuscles; besides, the detachment of portions of nuclear substance
seems in Limax irreconcilable with the early relations of nucleus and
aster. It seems unsatisfactory to consider the areal corpuscle as un-
modified “nuclear substance,” exercising an attractive influence on the
surrounding protoplasm, since the remaining and major portion of that
substance gives no evidence of exercising a like influence on the yolk.
I am therefore inclined to regard the corpuscles as a product of the
fusion of nuclear and vitelline substances.
Their ultimate fate is as uncertain as their origin. There is reason
for believing, from evidence given elsewhere, that in Limax the corpuscle
MUSEUM OF COMPARATIVE ZOOLOGY. 533
of the external half of the archiamphiaster becomes fused with the en-
velope of the polar globule at its distal pole. Whether the correspond-
ing corpuscles of the deep aster are also excluded from participating in
the formation of the new nucleus is more doubtful, but certain appear-
ances (Figs. 58, 60) favor the view that they may persist as discrete
bodies for a long time, perhaps till the new nucleus has acquired a mem-
brane. In that event they could hardly be employed in the nuclear
reconstruction without losing their morphological identity. As the area
more often appears homogeneous during the later stages of nuclear
growth (Figs. 59, 68, 93, 91) it is reasonable to assume that they are
ultimately redissolved.
There is one point in connection with the genesis of the asters accom-
panying the first segmentation which deserves particular attention. If
it could be shown that the rays of the “conjugation aster” are gradu-
ally altered in direction so that a portion became centred about one of
the poles of the first segmentation spindle, and the remainder about the
opposite pole, it would be strong evidence in favor of Hertwig’s view
that the radial phenomena are due to the attractive force exerted by the
nucleus upon the protoplasm, and that these forces, at first operating
uniformly in all directions, distribute themselves with the elongation of
the nucleus to its two poles. But the proof is not yet convincing; on
the contrary, it appears as though the asters at segmentation arise quite
independently of the “conjugation radiation.” The evidence that these
asters are due to the direct attraction of nuclear substance appears ma-
terially weakened by this want of continuity in their manifestations.
While I concur with Hertwig in the belief that there is an attractive
force exerted upon the vitelline protoplasm, which emanates from the
centre of the radiation, I would suggest that the force is generated by
the fusion of two unlike substances, — one of which is vitelline proto-
plasm, the other probably fluid constituents of the nucleus, — and not
by the attractive properties of either. Thus the attraction on the one
hand of protoplasm from the vitellus, and on the other of nuclear matter
from the nucleus (migration of lateral zones), may be effected by the same
force. But if it is nuclear substance alone which exerts the attractive in-
fluence, how shall it be explained that it attracts the nuclear disks ?
SprraL Asters. —I have designated as spiral asters certain peculiar
conditions often affecting the stellate figures connected with the elimina-
tion of polar globules. I have not met with anything in the observa-
tions of others which can be classed with these appearances. The rays
534 BULLETIN OF THE
of the asters in cell division have often been represented, since the time
of Auerbach (74, Taf. IV. Fig. 11), as being at certain stages curved,
but in none of them is the slight curvature of such a nature as to pre-
vent each ray from lying wholly in a plane. The rays of the spiral
asters are often much more prominently curved, and are not limited to
a single plane. But they also are not constant phenomena of any given
stage, nor of all asters. Therefore, whatever may be the cause of this
peculiar arrangement, it is not likely to be of fundamental importance.
The spiral condition will probably be instructive only in so far as it
throws light on the nature of asters in general, — on the physical state
of their rays.
The spiral course of the rays in the superficial (polar-globule) aster
might fairly be accounted for by assuming that it is caused by the force
which urges the tip of the maturation spindle into contact with the
envelope of the egg. The spiral form of the external aster would, then,
be only one of the results of its being compelled to adjust itself to an
altered position. What in one case is effected by a simple outward and
backward deflection of the rays producing the funnel-shaped figure, may
in this case be accomplished or aided by a lateral deflection. The spiral
course would evidently allow the centre of an aster with rays of fixed
length to approach nearer the surface than could otherwise be. If
this is the correct explanation, the spiral, like the funnel, results from
the force which impels the archiamphiaster against the resisting enve-
lope of the yolk. In one case the adjustment is accomplished by a sim-
ple bending of the rays, each of which continues to lie wholly in a plane
coinciding with the axis of the spindle ; in the other case the same end
is attained by the addition of another curvature which takes the ray out
of that plane.
This explanation would, I think, be entirely satisfactory if the phe-
nomena were limited to the superficial aster, but it is difficult to con-
ceive how a force (contraction ?), acting in any part of the yolk, could
induce such extensive spirals as are seen in the rays of the deep aster
of Fig 78. If the rays are the result of a constructive process, one
might assume that this construction advances in straight lines till it
reaches the periphery of the yolk, and that a deflection is then necessi-
tated on account of the resistance offered by the yolk envelope, — a resist-
ance that is sometimes overcome by the joint action of neighboring rays,
which thus cause pseudopodal elevations of the surface. This resist-
ance would then, it may be assumed, be propagated along the existing
portions of the ray, —such a transmission being rendered possible by
_ MUSEUM OF COMPARATIVE ZOOLOGY. 535
its semi-solid condition, — and effect an even curvature throughout
its length. Such an explanation would not be inconsistent with the
S-shaped curves sometimes (Limax, Fig. 57) seen. But the rays show
a spiral tendency before they reach the periphery, and those on the side
of the aster nearest the surface are no more curved than those on the
opposite side (Fig. 66). These are obstacles which are not readily ex-
plainable, for it is unsatisfactory to assume that the rays extend farther
than they are visible.
But whatever the view adopted regarding the cause of the spiral
arrangement of the rays, I believe there is great reason — both from the
spiral form and from the more simple deflection of the rays of the exter-
nal aster— for regarding them as something more than protoplasm in
a state of flux. It cannot be positively shown that either of the con-
ditions is not produced by the contracting influence of the hardening re-
agent until such arrangements shall have been observed in liwng eggs.
The same objections, however, hold good against considering these
asters artificial products, that have been so justly urged to prove that
asters in general cannot have been produced by reagents. Yet it still
remains possible to claim that the particular course of the rays in these
cases has been indirectly caused by the influence of the acids ; that, for
example, the immediate effect of the acid on the polar-globule protuber-
ance would be to diminish its capacity, and thereby compel the rays
to assume some other than the simple straight course they preserved
in the living state. The principal objections which can at present be
urged against this position are, — (1.) that the surface in this (polar-
globule) region shows less evidence of having suffered from a contrac-
tion than that of any other portion of the egg, for a diminution in the
capacity of the protuberance would imply a folding of its envelope, but
that is just what does not take place; (2.) that there is a progressive
modification of the direction assumed by the rays, which corresponds
with the advancement attained in the formation of the polar-globule
protuberance, so that the least deflection corresponds with the least
advanced condition of the elevation. Besides, no reasonable diminution
of volume could alone account for the extensive spiral of the deeper
aster. I am therefore of the opinion that this phenomenon is not
caused by the process of hardening, and that consequently it will event-
ually be found in living eges.*
* P. S.— Prof. C. O. Whitman of the University of Tokio, who had seen my
preparations previous to his departure for Japan, writes me (under date of June 18,
1880) concerning one of his students (Mr. lijima), engaged in studying the early
536 BULLETIN OF THE
Nuciear Sprnpite. — The fibrous cords which collectively form what
Biitschli named the “spindle-shaped body ” are intimately connected in
their origin with the asters. But to claim that they have only the same
significance as the rays of the latter, is not warranted by the observa-
tions. They are not only thicker, but they also pursue a different
course not strictly radial, and they exhibit special accumulations of
readily stainable substance ; they are principally composed of nuclear
substance, — the rays of vitelline protoplasm. While, then, I cannot
agree with Fol that the spindle fibres (bipolar filaments) are not dif
ferent from the unipolar filaments of the aster, and that they appear
different simply because enveloped in a different medium, there are still
grounds for a comparison. Since the centre of the aster, when it begins
to appear, often lies entirely outside the nucleus, the rays must, in such
cases, at first be formed exclusively in the yolk, and those which project
toward the nucleus are composed of vitelline protoplasm, as well as
those which radiate in other directions. The further growth of the
aster in the direction of the nucleus is really an encroachment of the
vitelline substance on the nuclear territory, just as O. Hertwig has
shown to be the case with the germinative vesicle and first maturation
spindle in Asteracanthion. Conditions such as are shown in Fig. 89,
Limax, also afford strong evidence that zn the beginning the rays which
eventually become spindle fibres are formed like the remaining rays of the
aster. They are rays which are formed outside the nucleus, or com-
mence outside, and, as it were, push their way into that structure. But
with that invasion is coupled the metamorphosis of the nucleus, so that
the latter is not to be regarded as simply a passive participant in the
changes. All accounts agree, I believe, in making the formation of the
spindle fibres progress from the poles of the spindle. In relation to the
centre of the aster, therefore, they erow like other rays, — in a centrif-
ugal direction. Their course, like that of unipolar filaments, is radial,
until, by increase of length, the rays from the two stars meet midway
to form the continuous bipolar filaments. Their course now becomes ~
slightly bent, so that, collectively, they present the appearance of a
cask.
Thus there exist many features suggestive of the identity of astral
rays and the initial condition of spindle fibres. It is a fundamental
question whether these fibres are ever constituted in any part of vitelline
stages of Nephelis: ‘‘His preparations show most distinctly what you discovered in
the egg of Limax, —curved radial lines. I can but wonder that Hertwig and
Biitschli did not recognize the same.”
——_—
MUSEUM OF COMPARATIVE ZOOLOGY. 537
protoplasm. Their centrifugal growth is not proof of it, but simply
makes it probable that the influence exerted from the centre of the
aster is cncreasing at the time of their formation, and that the substance
of which they are composed is affected in a manner similar to that of
the vitelline rays. An objection to this supposition is found in the
more common descriptions of the nuclear metamorphosis, in which the
asters are located at the boundary of the nucleus and vitellus, the former
being elongated into a more or less spindle shape. There is nothing in
this to suggest an incursion of vitelline substance ; besides, the spindle
fibres have been shown, especially by O. Hertwig, to be formed within
the nucleus when its lateral walls were still complete. At the ends of
the spindle-shaped nucleus, however, in all such cases, the nuclear boun-
dary has ceased to be visible, —the substances of nucleus and vitellus
are in contact. It therefore does not appear entirely impossible that
an invasion of slender threads of vitelline protoplasm might take place
at these points. But if they were just like the rays running through
the yolk, one would expect to find them traversing the whole space of
the nucleus, and not limited, as they have been shown to be in some
cases, to an axial portion.
It appears significant that the aster is never found to lie wholly
within the nucleus, but has been found wholly outside that structure.
Since, then, in some instances, there is no motive for ascribing to a
portion of the rays of the aster, in its early stages, a condition different
from the rest, J am led to the conclusion that the rays which stretch
through the nucleus are invasions of delicate filaments of protoplasm
about which the nuclear substance is progressively accumulated. This
may terminate in an intimate fusion of the two substances, or the latter
may exist as an investment of the former. I believe that the deport-
ment of the fibres at the time the nuclear disk divides offers some
support to the latter view.
The peculiar movements of the nuclear substance are perplexing. No
entirely satisfactory explanation of them has been given. With the
formation of the spindle fibres there is unquestionably a transfer of this
substance, not only to definite tracts indicated by the course of the fibres,
but also, and principally, toward the equatorial plane. Do these move-
ments occur in response to a force operating from the centres of the
asters? In view of the first appearance of the fibres at their astral ends,
this seems a reasonable assumption. The force must, then, be one of
repulsion for the nuclear substance. But that is not readily reconcilable -
with the subsequent division of the nuclear disk and the approach of
538 BULLETIN OF THE
this same substance toward the astral centres. There is nothing in the
appearance of the asters to warrant the conclusion that they at first
exercise a repulsive, and subsequently an attractive influence on the
same substance. Besides, the accumulation of the nuclear substance
along other portions of the spindle fibres than the equator seems most
naturally explainable as resulting from an attractive influence exerted
by the vitelline filaments, which, however, are presumably of the same
nature as the central mass of the aster, and ought therefore to operate
in the same manner on nuclear substance. The view that the equatorial
accumulation might be due to the mutual attraction of the elements
composing the nuclear disk, does not help to explain cases where (Limax,
Figs. 86-89) the segmentation spindle lies far to one side of the pro-
nuclei. Any scheme which admits that the substance forming the equa-
torial thickenings remains unaltered as regards its attraction or repulsion
for other constituents of the egg, encounters the fact that this substance
moves during successive periods in practically opposite directions. If
there were any means of making it probable that a change in the (elec-
tric or other) conditions of the nuclear substance itself takes place while
it tarries in the equator of the spindle, its movements might then be
explainable as the result of the uninterrupted action of a single polar
force, without involving the necessity of an entire reversal in the opera- —
tion of the hypothetical influence. But for the present I see no way of
accounting for a change in the nature of the moving substance which is any
more satisfactory than the assumption of a reversal of the moving force.
There is one feature in the migration of the lateral halves of the
equatorial thickenings which has, I believe, never been called in question
by any of the observers who have studied objects in which the migra-
tion could be readily observed in the living cell. The separation is at
first rapid, but subsequently the rate of the movement diminishes. The
bearing of this fact on the location of the forces which induce the sepa-
ration has not, so far as I recall, been stated by any one. It has more
generally been held that the separation is due to a traction emanating
from the centres of the asters, which draws asunder the halves of each
of these thickenings. Others have assumed that it was the result of the
mutual repulsion of the halves. So far as the rate of the separation is
concerned, it appears to me to support the latter view ; for, assuming, as
is most natural, that there is no rapid change in the intensity with
which the force acts, a diminution in the effect is what must necessarily
ensue with a constantly increasing distance between the source of the
force and the object moved. A gradually accelerated motion must, on
MUSEUM OF COMPARATIVE ZOOLOGY. 539
the other hand, be anticipated if the moving body is approaching the
source of the moving power. But if this should be proved inconsistent
with other phenomena accompanying nuclear division, it might be possi-
ble to refer the retardation to an increasing opposition to motion offered
by the substance in the vicinity of the astral centre.
The slender threads which remain behind the separating lateral zones
of thickenings, I have called, not to prejudge in the use of a name, znter-
zonal filaments. If the spindle fibres are, as has been generally maintained,
composed exclusively of nuclear substance, it is not apparent what these
interzonal filaments may be. It has been believed by some observers
that they represented a kind of product of the activity of the nuclear
substance of the fibres. It has been claimed that their substance,
like that of the thickenings, is ultimately employed in the growth of the
new nuclei, and that consequently they are nuclear substance. That
they differ from the spindle fibres and the varicosities is shown by their
not staining as intensely as the latter, and by the fact that they do not
as promptly respond to the force which causes the migration of the
stainable substance. While the evidence is too strong to allow a doubt
as to their being partly consumed in the growth of the new nuclei, [
think there is sufficient proof that the whole of their substance is not i-
corporated in the nucler. The evidence in Limax (Figs. 29, 80%, and 91)
is as satisfactory as could be expected in cases where the changes cannot
be directly observed. Neither their deportment with reagents* nor
their fate compels the belief that they are nuclear substance. I am
therefore disposed to believe that they are in composition like the
interstellate rays at their inception, — that they are, in other words, the
spindle fibres deprived of their nuclear substance, and that they differ
from the vitelline protoplasm with which they ultimately coalesce only
in their greater compactness and refringency.
Oriain oF Nuctet.— The formation of nuclei in early stages of on-
togeny results from a fusion of nuclear substance with protoplasm, and
occurs under two slightly modified forms. The production of the female
pronucleus is like that which takes place at each segmentation, and offers
no peculiarities capable of supplementing the knowledge of the process
which one may acquire from ordinary cell division ; but the origin of the
male pronucleus occurs under such different circumstances, that the
method of its formation throws additional light on the nature of nuclear
production.
* Compare Flemming’s statement, p. 360.
540 BULLETIN OF THE
As Auerbach first pointed out, the new nuclei in division arise in the
handle of the ‘‘dumb-bell.” The early observers who make the centre
of the aster the seat of the forming nucleus are unquestionably in error,
even if it must ultimately be granted that the “areal corpuscle” at the
centre of the aster forms subsequently an element in the new nuclear
structure. This corpuscle certainly cannot be looked upon as the begin-
ning of the new nucleus, which at an early stage lies at a comparatively
great distance from it. It has been shown by the observations of Biitschli
and Strasburger, and still more satisfactorily by those of O. Hertwig,
that the new nuclei arise directly from the lateral zones of fibre thicken-
ings, which, in turn, owe their existence to a rearrangement of nuclear
substance. My observations serve to confirm this for Limax.
How the metamorphosis of the lateral zones is effected has not been
so definitely established. Biitschli has claimed that the new nucleus
begins by the formation of a very small, clear, fluid-filled space around
the dark granules of each zone, and that the granules become the nwcleola
of the new nucleus. Certain features of the metamorphosis in Limax
seem to favor this view. A comparison of Fig. 90, where the first evi-
dences of a segmentation furrow are visible, with Fig. 93, where the
cleavage is only about half completed, shows that the changes in the
nascent nucleus must be at this period very rapid. The existence of a
large number of nucleoli in the second case is perhaps indicative of a
direct genetic connection between the “thickenings” and the nucleoli,
rather than a more radical metamorphosis out of which the nucleoli have
arisen as new formations ; and yet, in any event, time enough has elapsed
for a considerable increase of the nuclear mass, as the size of the new
nuclei clearly shows. In later segmentation stages, especially during
the second cleavage, I have more satisfactorily observed the early condi-
tion of the nucleus, — most distinctly after treatment with osmic acid
and Beale’s carmine. When of about the size of the lateral zone in Fig, 90,
it appears as a small uniformly stained homogeneous body. The pro-
nuclei (Fig. 70°) are also sometimes encountered in a homogeneous con-
dition. But the rarity with which these stages are found lead me to
think they are of exceedingly brief duration.
It is generally conceded that the nucleus is composed of at least two
substances, which present properties different from each other and from
the protoplasm of the cell. They have been designated by R. Hertwig
as “ Kernsubstanz” and “ Kernsaft.” O. Hertwig has explained the for-
mation of the new nucleus as due to a process the reverse of that which
takes place at the formation of the rods composing the middle zone of
le
MUSEUM OF COMPARATIVE ZOOLOGY. 541
thickenings. Whereas in the latter case there is a severing of these two
constituents of the nucleus, in the former the nuclear substance, still
in the form of rods, imbibes nuclear fluid, and the individual rods,
swollen into granules, then become confluent, and thus is restored a
nuclear mass of uniformly mingled constituents. So far as my observa-
tions extend, they do not directly conflict with Hertwig’s views; but,
theoretically considered, it seems difficult to explain what the signifi-
- cance of all this metamorphosis may be, if the same fluid constituents of
the old nucleus ate to be reabsorbed by the accumulations of readjusted
nuclear substance. It appears to me much more reasonable to assume
that that which is appropriated by the lateral zones is new substance
from the neighboring protoplasm, and even not exclusively the more
fluid constituents of the latter. If Hertwig’s statements do not imply
the reabsorption of the nuclear fluid set free at the disappearance of the
membrane of the old nucleus, then I can accept his interpretation ; for
he says of a somewhat later stage, to explain the growth, that the nucleus
possesses the ability to appropriate from the yolk “ fliissige und feste
Stoffe.” But what may be said of the young nucleus in this respect
may also be reasonably ascribed to the nuclear substance existing in the
rodlike form. It appears to me certain, from the increase in the total
mass of the nuclei with successive segmentations, together with the
absence of evidence that the proportion of ‘nuclear substance” is corre-
spondingly diminished, that the nuclear substance of the “ thickenings,”
and afterwards the young nuclei, possess the ability to incorporate with
themselves, not only the more fluid constituents from the yolk, which
may represent the “ Kernsaft,” but also less fluid portions, which with
equal propriety may be considered ‘“‘ Kernsubstanz.” That the central
areas of the asters, when such exist, sustain an intermediary relation
between the protoplasm on the one hand, and the growing nucleus on
the other, can hardly be questioned. It is a significant fact, that the
fusion of these zonal rods into a homogeneous body only takes place
when the latter have reached, not the apex of the spindle, but the edge
of the “area,” and are thus in a situation to avail themselves directly
of the areal substance. Whether the latter is unaltered protoplasm,
or whether it is protoplasmic substance which has already undergone
changes rendering it more like that with which it is about to be incor-
porated, is not to be answered categorically ; but the signs of chemical
activity developing a force which affects the remotest portions of the
vitellus are indicative of fundamental changes in the region of these
areas, and the properties of their substance which have been observed
542 BULLETIN OF THE
by Whitman (his “nucleoplasm”) and others point in the same di-
rection.
O. Hertwig has shown experimentally in the starfish, that, when fecun-
dation is introduced before the formation of the female pronucleus, the
male pronucleus attains the same dimensions as the female; but when
fecundation is delayed until after the female pronucleus is developed, it
remains much smaller than the latter. The explanation implied in
Hertwig’s statements is, that in the latter case the female pronucleus
has already appropriated, as it were, the whole of the: available nuclear
fluid. The same theory Hertwig thinks valid in explaining constant dif-
ferences in the relative sizes of the pronuclei after normal fecundation in
different animals. Thus in Toxopneustes, where the events of matura-
tion transpire before fecundation, the male pronucleus remains small,
while in mollusks, etc., spermatization having been effected before these
events, the two pronuclear bodies attain the same size. In so far, then,
as this theory serves to explain phenomena, it establishes its claim to
acceptance. But there exist certain objections to this view. It seems
to necessitate the belief in a fixed amount of unengaged nuclear fluid,
which, I believe it is fair to assume, the author must identify with that
which was liberated at the metamorphosis of the germinative vesicle.
That being the case, the theory necessitates the wniform diffusion of this
liberated fluid through the whole yolk ; as, otherwise, how could a male
pronucleus, arising indifferently at any point near the surface, enjoy the
same opportunity for the acquisition of it as a female pronucleus origi-
nating in the immediate vicinity of the place where it was set free?
Although the male pronucleus has been seen before the formation of the
first polar cell, it does not appear that it increases much in size, or is far
removed from the surface of the yolk, before the production of the second
polar cell; that is, before the time the substance of the female pro-
nucleus loses its connection with the substance of the last polar cell. —
It then exhibits a more or less rapid growth and migration. But if it
is simply dependent for its increase in size on the liberation of nuclear
fluid, I see no reason why it should not greatly increase, even before the
production of the first polar cell, in cases where the spermatization is
effected before the events of maturation. And if Hertwig’s reasoning
is correct, why should it not, in these instances of early fertilization,
acquire the major portion of the available nuclear fluid, and thus sur-
pass in size the female pronucleus, instead of simply reaching an equal-
ity with it? May it not be that differences in the growth of the male
pronucleus are explainable without recourse to the supposition of a fixed
MUSEUM OF COMPARATIVE ZOOLOGY. 543
amount of nuclear fluid? Its increase in size appears to be intimately
connected with its migration, and the migration is apparently in response
to the direct attractive influence of the female pronucleus, with which it
is ultimately fused. In cases where the latter has attained its full size,
its power of attraction will be greater, as its mass is greater, than at
any earlier period in its growth, and the migration of the male pro-
nucleus will be correspondingly more rapid, so that it will have less
time to incorporate with itself substances from the protoplasm. It will
reach the female pronucleus before it has acquired its normal size; but
this it may subsequently attain by continuing to grow after encountering
the latter, as Selenka has shown to be the case in Toxopneustes, This
may perhaps explain the experimental cases, as well as that of Toxo-
pneustes, where the female pronucleus takes a position in the centre of
_ the yolk. It cannot, however, be claimed that migration and growth
stand in the relation of cause and effect, since in certain cases (eccentric
female pronucleus), when the male pronucleus arises near the animal
pole, the extent of its migration is more limited than when it makes its
appearance near the opposite pole; and yet it attains in both cases the
same dimensions, and probably grows with the same rapidity. It can
be said that both migration and growth appear to depend on the exist-
ence of certain conditions which are established with the elimination of
the substance of the: polar globules, but not that those conditions are
fulfilled by the liberation of nuclear fluid at the time of the conversion
of the germinative vesicle into an amphiaster; for the observations of
Whitman on the “quiescent state” of the egg in Clepsine seem to afford
the most satisfactory proof that the metamorphosis of the vesicle may
transpire long before the enlargement of the male pronucleus, and
nearly all observers concur in the statement that the two pronuclei
arise at nearly the same time in cases where spermatization has preceded
maturation.* From this it appears to me that the growth of the male
aster, instead of corroborating, offers serious obstacles to the acceptance
of Hertwig’s explanation.
* From the evident dependence of the migration and growth of the male pro-
nucleus on the existence of a more or less developed female pronucleus, it appears
reasonable that with the detachment of the polar cells the character of the nuclear
substance is so far altered that it exerts on the male pronucleus an attraction of
which it was incapable when still joined to the nuclear substance that is removed
with the polar cells. Whether this implies a greater difference than exists between
the halves of the nuclear plate in ordinary cases of cell division, may be questioned.
It should at least be remembered that there are in all cases indications of a mutual
repulsion between the lateral zones of fibre thickenings.
544 BULLETIN OF THE
There are probably at least two modifications of the process by which
the fibre thickenings are converted into a single nuclear structure. It
has been repeatedly shown, that in some instances the individual thick-
enings pass through a vacuolar stage, and that nucleolar bodies are found
in the vacuoles before their ultimate confluence, —the “ multinuclear”
condition of the cell. In Limax I have been unable to detect such a
condition, and am therefore inclined to believe that the differentiation
of nucleoli does not take place until after the fusion of the thickenings.
But this difference is not one of fundamental significance, since in cases
where clusters of nuclei are developed their confluence in some instances
regularly ensues much earlier than in others. Limax, then, only fur-
nishes one of the extreme examples, since here the confluence takes place
before the formation of nucleoli. The postponement of the fusion,
observed in so many cases, and the consequent presence of a number of |
apparently unconnected vacuolar structures, no more warrant the con-
clusion that a multinuclear condition exists than does the earlier state,
when the nuclear substance consists of a group of more numerous fibre
thickenings. It is only a stage in the process of concentration into a
single nucleus, and these different phases under which it occurs only
serve to make this interpretation more reasonable. In all cases of a
spindle differentiation the processes are essentially the same; there is
a fusion of the nuclear substance of the thickenings with the protoplasm
of the yolk, and the end result is a single nucleus.
The proportion of the nuclear substance from the old nucleus, which,
by means of the “ thickenings,” directly contributes to the formation of
the new nuclei, although approximately constant for a given stage in the
development of any given animal, is subject to wide variations from one
animal to another; and there exist even more extreme modification,
between remote cell-generations in the same individual. In Limax,
where the nuclei attain a large size, the proportion is very small, espe-
cially in the formation of the male pronucleus, if, as is probable, the latter
is initiated by a single spermatozodn ; somewhat greater in the star-
fish and the Hirudinea, for example, where the nuclei remain compara-
tively small. But in plant cells the proportion is often very large, and
in certain tissue cells, as Flemming has shown, almost a maximum.
Whether there exist cases in which the old nucleus simply divides
without any metamorphosis, — without the least interchange of sub-
stance with the surrounding protoplasm, — and, if so, whether the condi-
tions prevailing in tissue cells present stages of transition between the
more direct and the more complicated methods of nuclear division, —
MUSEUM OF COMPARATIVE ZOOLOGY. ; 545
can be satisfactorily answered only by further and extensive comparative
studies. There are already many important observations which make
such a direct division (without fibrous differentiation) probable; but
even in such cases an interchange of substance may not be completely
excluded, and the certainty that there is an increase in the total amount
of nuclear substance with successive generations makes the acquisition
of new material on the part of the nucleus unquestionable. That this
acquisition is facilitated by the division may at least be claimed as
probable.
It is extremely doubtful whether new nuclei arise in animal cells
without the least visible connection with the nuclear substance of pre-
existing nuclei. Even in plant cells this process may be less certain
than has been claimed. I have endeavored to show how the case of
Isoétes might possibly be less indicative of this mode of formation than
Strasburger teaches ; but the evidence from the conifers and from Pha-
seolus seems at present capable of no other interpretation than that
there is often a complete dissolution — a morphological obliteration —
of the old nucleus. It perhaps is not entirely unreasonable to indulge
the hope that even in these cases new methods of investigation may
ultimately prove that there is not an entire dissipation of the substance
of the old nucleus. In either event, however, the interpretation which
Strasburger has given is that which most fully explains the extreme
cases.
GERMINATIVE VeESIcLE.—It has been conclusively shown both by
Fol and by O. Hertwig, that the first maturation spindle is formed at
the expense of constituents of the germinative vesicle. The latter is
neither totally dissolved in the yolk nor totally eliminated from the egg.
I have not proved the same to be the case in Limax; but there is no
occasion to doubt that the first archiamphiaster is there produced in the
Same manner as in the starfish. So much being granted, there is every
reason to agree with Hertwig that a genetic connection exists between
the germinative vesicle and subsequent generations of nuclei. I have
never found an egg which did not, under proper treatment, exhibit some
definite morphological evidence of the existence of a nuclear structure,
and am certain that in no case is the formation of the polar globules
accompanied by an elimination of the whole of the spindle. The female
pronucleus is formed primarily from the inner half of the nuclear plate
of the second maturation spindle, and its substance enters into the com-
position of the first cleavage spindle. The evidence of the continuity
VOL, VI. — No. 12. 35
546 BULLETIN OF THE
of the substance of the germinative vesicle with that of the nucleus of
the first segmentation sphere, is as complete as could be expected of
eges which do not allow the demonstration of the spindle nucleus in the
living condition. I have been led to suspect that certain phases of the
metamorphosis — between the first and second maturation spindles —
have not yet been discovered ; but I have no evidence that such a hypo-
thetical stage renders this continuity any less certain. On the contrary,
if such an intermediate stage as I have suggested really exists, it can
have no other effect than to remove the nucleus of the first cleavage
sphere one generation further from the germinative vesicle, but does
not even warrant the supposition that the former contains a smaller pro-
portion of the nuclear substance of the vesicle than it would have con-
tained had the course of events been such as recent observers, who admit
the continuity in question, have claimed. But it is not a question of
the amount of nuclear substance which thus finds its way into the nuclei
of successive generations. The continuity is definitely and adequately
established by the fact that generation after generation the nuclei
have for their beginnings portions of the substance composing the-
nuclei of the stage preceding. There is not the least doubt that such
beginnings exist in the lateral zones of fibre thickenings. The stage
in the process which is least satisfactorily understood is that of the
origin of the equatorial zone. There can be little question that it is
formed in the same manner in all the earlier embryonic stages at least,
and it is equally evident that it must in some way be formed at the
expense of the disappearing nucleus. My own observations (Figs. 85-
89) support this view in a decided manner. Whether, however, any
portions of the old nucleus — and, if so, which — go over bodily and
unaltered into this forming disk, seems much less certain. Hertwig’s
studies assuredly offer the best evidence we have that such is the case ;
but Hertwig has failed to demonstrate that the beaded elements of the
nucleolus are directly incorporated in the equatorial thickenings. He has
traced them as far as the central area of a forming aster, but that is not
the equator of an amphiaster. His observations only strengthen his
position that it is the nucleolus (and therefore “nuclear substance”)
which is immediately concerned in the building up of the nuclear spindle,
and do not necessarily prove that it persists in the shape of fibre thick-
enings. I have once seen appearances (Fig. 85) which suggest that the
substance of these thickenings may be aggregated into definite visible
corpuscles in the region of the nascent spindle, independently of the
fibres to which they ultimately belong; but I place little confidence in
MUSEUM OF COMPARATIVE ZOOLOGY. 547
this observation, and prefer to rest in the tentative belief that the thick-
enings are produced solely by molecular rearrangements of the nuclear
substance, which is accumulated along the protoplasmic axis of the
fibres. This view is not to be confounded with Auerbach’s karyolysis,
for it does not involve a dispersion of the substance of the nucleus
through the neighboring protoplasm, and its re-collection. It implies a
direct transfer of substance, but in elements too small to be individually
visible even with the best optical aids.
Potar GLoBuLes. — The formation of polar globules has been shown
to be a constant feature in the maturation of eggs in representatives of
a majority of the recognized groups of animals. It is principally in
such as are characterized by the possession of a large proportion of nu-
tritive substance that their presence has not been established. The in-
creasing evidence of their constant production warrants the assumption
that they will be discovered in many cases, perhaps even in the larger
groups, where they have not yet been seen. The great probability of
their formation in Tunicata has been shown from the figures given by
Strasburger.* Still, the thoroughness with which some groups have been
* P. S. — Grobben ("79, p. 209) has shown that in one of the Cladocera (Moina)
there is imbedded in the yolk at the animal pole of recently excluded eggs a body
which stains intensely in carmine. He believes it is a polar globule, which in this
case has not been detached from the yolk. This is perhaps the best evidence yet
produced to prove the existence of polar globules in Crustacea, and with further study
may possibly serve to show some of the regressive steps by which their production
has sunk from the dignity of cell division to a simple elimination of an amorphous
mass at the primary pole of the yolk. I would call attention, however, to the pos-
sibility of a close relationship between this body and the polar accumulation of stain-
able substance (polar ring) described by Whitman in Clepsine. The indistinctness
of its limitation from the yolk (oc. cit., Fig. 3), and its not protruding above the
surface of the same, are points of resemblance with the polar rings ; but its persist-
ence in late stages of segmentation (Figs. 5, 6) seems at first to indicate a different
fate from that of the ring substance. But when there are fifteen blastomeres, the
small sphere which contains the ‘‘ Richtungskérper” is divided by an equatorial
plane into two spheres of equal size, and Grobben adds (p. 212): ‘* Mit dieser Thei-
lung verschwindet der Richtungskérper von der Oberfliiche des Hies, da er offenbar
in die Tiefe der oberen Furchunyskugeln gelangt.”
This seems to afford strong indications of the identity suggested, and, if once estab-
lished, may remove Grobben’s doubt as to the polar-globule nature of the bodies de-
scribed by Leydig (60, p. 145) for Daphnia longispina as “ einige blasse Kiigelchen,
ganz vom Charakter jener unter dem Namen ‘ Richtungsblaschen’ beschriebenen
Gebilde,” which he saw appear ‘‘an dem einen Pol ausserhalb der Eischale.” It is
noticeable that at the first segmentation this body (Grobben, Fig. 2) remains in con-
548 BULLETIN OF THE
studied with this point in view, and especially the presence of conditions
at maturation which appear to be, if at all comparable with, at least
fundamental modifications of this process, seem to preclude the exist-
ence of typical polar globules in a number of the groups of animals,
while the failure to find equivalents of the “canal cells” in the higher
phanerogams is possibly even a greater obstacle to the claim that they
are of universal occurrence.
The fact that it is the eggs possessing a large proportion of nutritive
substance which deviate from the typical formation of polar globules
would indicate that it might be the accumulation of this food material
which interferes with the normal or more primitive method of matura-
tion, and prevents the formation of cell-like polar bodies. There seems
little doubt that the elimination of portions of the substance of the
germinative vesicle as described by Balfour for Elasmobranchs, by
Oellacher for bony fishes * and birds, and by Van Bambeke and Hert-
wig for Amphibia, represents in some hitherto unexplained manner the
formation of polar globules. It is perhaps safe to indulge the expecta-
tion that some of the representatives of these groups will ultimately
furnish the means of explaining how the two processes are reconcilable :
at present it does not seem possible to present a satisfactory hypoth-
esis of their mutual relationship. It can only be said that in all cases
there is probably an elimination of a part, and of only a part, of the
substance of the germinative vesicle together with a small portion of
nection with the blastomere, which appears to be a trifle the larger, — just as in Clep-
sine the oral-ring substance does (compare Whitman 78%, Fig. 15), — and which
takes the lead in the production of the small cells about the primary pole, exactly as
Whitman (Figs. 19, 20) has shown to be the case in the leech. That the ringlike
disposition of the substance is in no way a necessary feature follows from the con-
dition (Whitman, Fig. 70) presented by the ‘‘aboral ring.” This, however, is no
argument for the identity of Grobben’s body with polar rings, since the polar globules
sustain in Clepsine the same relation to the blastomere which leads in segmentation.
Henneguy (80) has also reported the discovery of polar globules in one of the
Crustacea (Oniscus).
* P. §. — Hoffmann (’80) has given a preliminary account of the early stages of
several osseous fishes, in which he shows that a single polar globule is produced in
the normal way from the external half of a maturation spindle. He claims, however,
that, as the nucleus which is formed from the inner half of this spindle is the
‘‘ Hikern,” so the nucleus which is formed from the external half is the ‘‘ Richtungs-
kérperchen.” Can it be that this represents a transition from a process where the
production of polar cells entails the loss of a certain portion of the yolk to one where
there is an elimination of only nuclear material, or is it to be assumed that Hoffmann’s
statement is, from its brevity, slightly inexact ?
MUSEUM OF COMPARATIVE ZOOLOGY. 5A9
the vitellus. In the case of mammals there is sufficient evidence of the
existence of polar globules, as the early studies of Bischoff indicate, but
no one seems to have yet discovered the method of their production,
and it is therefore open to question whether they arise by a process of
cell division from the external halves of maturation spindles. Ed. van
Beneden’s account for the rabbit does not remove the uncertainty.
There are, besides, two other groups of animals in which the presence
of anything ¢ven remotely comparable to polar globules has not yet
been satisfactorily determined, — Rotifera and Arthropoda. Flem-
ming’s expectations in regard to the existence of the polar globule in
Lacinularia were not confirmed by Biitschli, who directed particular
attention toward their discovery in the Rotifera. The accounts of their
formation in certain Crustacea * also need further confirmation.
The polar globules may be considered from three standpoints, — the
morphological, the physiological, and the historic, or phylogenetic.
Morphologically viewed, there can no longer be any doubt that they
are cells. They are formed by a process in all essentials like ordinary
cell division. They are composed of a protoplasmic substance which
stains feebly, and of a nuclear substance which stains deeply. The lat-
ter is derived, through the intervention of a fibrous spindle and a divid-
ing nuclear plate, from the nuclear substance of the immature ovum.
The lateral zone of thickenings in the globule is not always massed into
a single nuclear structure. It is possible that in many cases this con-
dition is exhibited because sufficient time has not elapsed for the accom-
plishment of the successive acts of the consolidation. But in any event
the conclusion seems inevitable that there is a decline in the functional
activities of this cell, which delays the completion of its work beyond
the normal period of such changes. It is probable that many polar
cells never would have attained this typical condition, — a cell with a
single nuclear structure, —even if their activities had not been inter-
cepted by the action of reagents. A decline in the functional potency
of the polar cell is ultimately followed by a complete surrender of its
morphological integrity. That, however, does not warrant a denial of
its morphological value as a cell, any more than the gradual obliteration
of the structure of an element from the epidermis would justify a de-
nial of its cell character.
Notwithstanding the cell nature of the polar globule, there is one mor-
phological peculiarity connected with its production, besides its diminu-
tive size, which has been previously observed, it is true, but which has
* Consult Leydig ’60, p. 145; Dieck "74; and Hoek ’76, p. 62.
550 BULLETIN OF THE
not been sufficiently emphasized. This unique feature is the coalescence
of the “areal corpuscle” of the external aster with the envelope of the polar
cell at its distal extremity. It is a peculiarity which may perhaps be of
importance in two ways. It is possible that it will some time help to a
better understanding of the forces at work in the process of cell division,
and it may also be of importance in deciding what share the “ areal
corpuscles” of the stellar figures take in the formation’ of new nuclei.
O. Hertwig is, so far as I am aware, the only observer who has given any
representation of such conditions as I find in Limax. In the cases
especially of Nephelis and Heemopis he (’77, Taf. I., II.) has figured the
tip of the spindle as lying at the surface of the ege, and he mentions
(p. 20) ‘ein dunkles Korn, die peripher gelegene Spitze der Spindel.”
The figure referred to in this connection (Taf. II. Fig. 3) is perhaps in
this particular the least satisfactory of all those given by Hertwig ; for
the “ Korn,” although represented as being “ peripheral,” is not in con-
tact with the outline of the polar globule. If the apex of the globule
were turned a little toward the observer, so as not to be seen exactly in
meridional section, the ‘“ Korn” might appear, as it does in his figure, at —
some distance from the surface (i. e. from the outline), even if fused
with it. One hardly has the right to assume that so skilled an ob-
server could have mistaken the position of this conspicuous granule ;
otherwise I should conclude that in this case, as in a majority of the
egos represented, the tip of the spindle (its “‘ Korn”) was merged in the
envelope of the polar cell. That such is really the case in Limax I have
not the least doubt. Evidently, then, zn the polar cell, the “ areal cor-
puscle” takes no part in the formation of the new nucleus. 'The question
naturally arises, In how far are the conditions realized in the polar
cell duplicated in the egg cell? If the areal corpuscle contains nuclear
matter, and is essential to the completion of the new nucleus, how can
it so completely fail to realize its true destiny in the polar cells? Al
though I can consider the question hardly more than fairly stated, still
there are some features in the formation of new nuclei, already dis-
cussed, as well as certain facts concerning the place where these “ areal
corpuscles” first appear, which lead me to think that it may not be
necessary to interpret the latter as nuclear substance. Such a view
might cause this peculiarity of the polar cells to appear less bizarre.
The relation of the centre of the external aster to the envelope of the
polar cell is certainly unlike its relation to that of segment spheres in
ordinary cell division ; for there is no case, however small one of the
products of segmentation, in which the centre of the aster approxi-
MUSEUM OF COMPARATIVE ZOOLOGY. Bo
mates the outer wall of its cell. This is a peculiarity in the formation
of polar cells which deserves more attention than it has received. It
may perhaps be urged as an indication, that the production of polar
globules is not accomplished by cell division; but it appears to me
that it does not present any fundamental obstacle to that conception.
In an examination into the nature of the forces which result either
in the production of the polar globule or in cell division, this peculi-
arity may furnish some means of extending or correcting conclusions to
be drawn from less modified forms of division. |
No theory of a mutual repulsion between the stars of the amphiaster
is able to explain either the “‘ orientation” of the spindle, or its migra-
tion to the surface, nor is the existence of such a repulsion at this stage
certain, since the length of the spindle (with a single exception, no-
ticed later) remains during this period practically unchanged.* Neither
does it seem possible to explain the migration as due to the attrac-
tion which the centres are supposed to exercise on the vitelline proto-
plasm, even if such an attraction were capable of putting the spindle
in a central position in reference to the active constituents of the vi-
tellus, or of causing it to occupy the primitive axis of the yolk. No
such attraction could urge both asters into such close approximation
to the animal pole. There may be complicated chemical and physical
processes underlying all the movements connected with the formation
of polar globules which are at present as unintelligible as are all other
spontaneous movements of protoplasm. Still it is not useless to inquire
whether there is any possible explanation of the movements of the
archiamphiaster which, without dealing with the nature of protoplasmic
motion in general, is capable of rendering these changes less obscure.
An assumed attraction, exerted by the protaplasm upon certain con-.
stituents of the spindle (the inner half), and a repulsion of other con-
stituents (external half), would be sufficient to cause the “ orientation ”
of the spindle in the primitive axis; but a migration which carries its
internal end beyond the centre of the active protoplasm toward the
primary pole could only be accomplished by the repulsion preponderat-
ing over the attraction, and even with that assumption a lengthening
of the spindle should result from the repulsion of one of its ends and
the attraction of the other. The final separation of the repelled portion,
accomplished by the formation of polar globules, would then leave the
* In the early stages of its formation a mutual recession of the asters has been
observed, and may perhaps be attributed to the development of mutually repulsive
properties, but after the formation of the spindle there is no important separation.
552 BULLETIN OF THE
attracted portion free to move in the direction of the centre of the at-
tracting protoplasm, be that the centre of the yolk or a point nearer
the animal pole. The case of the migration of the germinative vesicle
before its constituents are converted into a spindle would demand no
special modification of the assumed forces. The most serious objections
to this explanation are the constancy of the distance between the asters
during the migration and the entire similarity of the lateral nuclear
plates, both in size and behavior, which appears incompatible with their
being affected in different degrees by the assumed attraction and re-
pulsion. ;
Simple contractions on the part of the vitellus might under certain
circumstances produce the same result. If the yolk presented in its
primary radius a structural condition which offered less resistance than
other radii to the progress of a moving body, any contractions of the
vitellus would cause the amphiaster to passively advance along this
radius until it reached the surface, and finally cause its protrusion.
That this is structurally different from other radii is sufficiently obvious
in many cases, but I do not know that there is any direct evidence of —
the condition (more passable) assumed. This would make the whole
amphiaster entirely passive as far as regards the migration, and it would
afford no explanation of the cause which induces the return of the inter-
nal half of the spindle toward the centre of the egg as a female pro-
nucleus. It may be of some importance in this connection to know
just when this migration of the amphiaster takes place. Whitman has
shown that a quiescent stage may intervene between the formation of
the first archiamphiaster and that of the first polar globule; but I am
not quite certain how far the egg has advanced when this interruption
of activities is manifest. It seems most likely from his account that
although the “ polar figure” (which results from the presence of one of
the asters near the surface) makes its appearance, the centre of the
external aster does not reach the surface until after the egg emerges
from its quiescent state. At least, he does not mention the existence
of the “ pellucid spot” at this stage, and states that it usually appears
from ten to twenty-five minutes after the egg is deposited. It is there-
fore probable that the contact of the astral corpuscle with the limiting
envelope of the egg takes place during the series of vitelline con-
tractions which terminates in the production of a polar cell. These
contractions have been shown to assume in Clepsine a most remarkable
and uniform appearance, —a constriction advancing from the equator
toward the primary pole. It is not to be claimed that the migration of
MUSEUM OF COMPARATIVE ZOOLOGY. 553
the spindle is accomplished directly by the movement of this wave-like
constriction, for the pellucid spot is seen before the wave has begun to
approach the primary pole of the egg. It is only probable that the
migration is accomplished by contractions of the yolk, of which this is
a special manifestation, and moves toward the animal pole, because that
radius corresponds with the line of least resistance. Evidences of con-
traction are not so marked in Limax, but still they are exhibited in
alterations of the general form of the egg, and especially in the con-
stancy with which the primitive axis is shortened. (Compare also
Fig. 55.)
But whether it be the result of a repulsion, due to physical or chemi-
cal conditions of the substances concerned, or simply of the contraction
of the yolk, the amphiaster certainly appears in this movement to be
more acted upon than acting. There must be some influence operat-
ing from behind to account for the deflection of the rays of the outer
aster, and it is probably the same force which induces the shortening
of the spindle observed by O. Hertwig in Asteracanthion just before the
formation of the polar globule.
The physiological significations which have been attached to the
polar globule have differed widely, from an important determining in-
fluence upon the course of subsequent events in segmentation to a
meaningless exudation of liquid from the yolk. While its morphological -
place is well established, it does not of necessity follow that its function
is explainable from the same data. It may not be as rational now to
say that it is without meaning, as it was when Rathke pronounced that
verdict ; but its being a cell will not be found sufficient evidence that it
is not the means of removing useless or undesirable material. It soon
undergoes disintegration, and certainly has no further importance in
the economy of the embryo: these have been brought forward as evi-
dences to support this view. That its present functional importance
consists only in the removal of certain substances from the egg receives
further support from the continuance of the process of removal in cases
(Batrachia, etc.) where the cell condition is no longer maintained. But
an objection to any view which discovers in this phenomenon only
the removal of worn-out material is that the removed substance par-
takes of the nature of the cell in every essential particular. It cer-
tainly embraces nuclear substance and more or less granular protoplasm.
The changes which accompany its formation are, save in one or two
minor points, like those which accompany ordinary cell division; its
nuclear substance assumes the same conditions (though not so promptly)
554 BULLETIN OF THE
as the nuclear substance in the remaining portion of the egg. There
are some indications that its substance acts less vigorously than that of
the larger cell, but it certainly has not lost all its reconstructive ability.
It is therefore unlike any known products of secretion or defecation.
Biitschli has advocated the opinion that the principal physiological
signification of the globules consists in the removal of a part of the
“‘ Kikern” (germinative vesicle) ; and Strasburger adopts the same view
in saying that the nucleus frees itself of certain constituents, and thus
makes ready for the approaching fecundation. Biitschli’s opinion that
this elimination is due to fecundation, or is at least a phase in the early
development of the egg, not in its maturation, must be abandoned, since
it has been shown that the globules are in many cases formed before
the approach of spermatozoa. It seems, however, to be indicative of a
mutual influence of spermatic and polar-globule substances, that the
male pronucleus is retarded in its migration and growth up to the time
of the detachment of the second globule, as though the presence of the
polar-globule substance acted as a hindrance to its normal development.
Balfour has adopted nearly the same view as Biitschli. He explains
the act as consisting in the removal of parts of the germinative vesicle,
more or less essential to the further independent development of the
cell, to make room for the supply of the necessary parts to it again by
the spermatic nucleus. This hypothesis would serve, he thinks, to ex-
plain why it is that polar globules have not been found in those groups
(Arthropoda and Rotifera) where parthenogenesis is most frequently
encountered. The fact that parthenogenesis is possible where impreg-
nation is the normal occurrence, may appear, he says, to be an objec-
tion ; but it cannot be denied without further study that development
in such cases may be due to the suppression of the globules, and that
when they are formed development without impregnation is less
possible.
An objection to this latter assumption is the tardiness in the events
of maturation which must be admitted when fecundation is under the
control of the parent. If there were a suppression of the polar globule
in the case of unimpregnated eggs of the honey-bee, for example, then
the first steps in the formation of the globule must normally take place
after the egg has passed the seminal receptacle, for the fecundation or
non-fecundation of any given egg is not previously determined. In
other words, the development of the egg up to that epoch must be the
same in all cases, whether a polar cell is to be formed or not. Such a
delay in the events of maturation may not be impossible, but does not
MUSEUM OF COMPARATIVE ZOOLOGY. 555
appear very probable. If the polar globules exist simply to remove an
essential substance in order that another essential element may take its
place, the whole process would appear to be a waste of energies with
which nature is not often chargeable, unless it can be shown that some
serviceable end is reached by such an exchange.*
None of the physiological interpretations offers any explanation of the
most characteristic feature of the polar globule, —its cell nature. Evi-
dently, any theory to be entirely satisfactory must explain the signifi-
cance of this fact. Even if it be granted that its present function is
one that may be accomplished without its assuming the condition of a
cell, it will be useless to attempt to elucidate its full meaning without
recognizing the importance of that peculiarity. The constancy of this
morphological characteristic points to one of two things ; either there is
some peculiarity in the present function of the globule, which is best
subserved by a cell-like structure, or it is simply the heritage from a
former state in which the polar cell may have had a different functional
signification from that to which it now responds.
* P.S. — Balfour (’80, p. 63) suggests ‘‘that the function of forming polar cells
has been acquired by the ovum for the express purpose of preventing parthenogenesis.”
His reasons for this conclusion are stated as follows: ‘‘The explanation given by
Mr. Darwin of the evil effects of self-fertilization, viz. the want of sufficient differen-
tiation in the sexual elements, would apply with far greater force to cases of par-
thenogenesis.”
‘Tn the production of fresh individuals, two circumstances are obviously favorable
to the species: (1.) That the maximum number possible of fresh individuals should
be produced ; (2.) That the individuals should be as vigorous as possible. Sexual
differentiation (even in hermaphrodites) is clearly very inimical to the production of
the maximum number of individuals. There can be little doubt that the ovum is
potentially capable of developing by ztse/f into a fresh individual, and therefore, un-
less the absence of sexual differentiation was very injurious to the vigor of the
progeny, parthenogenesis would most certainly be a very constant occurrence ; and,
on the analogy of the arrangements in plants to prevent self-fertilization, we might
expect to find some contrivance both in animals and in plants to prevent the ovum
developing by itself without fertilization. If my view about the polar cells is cor-
rect, the formation of these bodies functions as such a contrivance.”
Why the eliminated substance takes the form of a cell, still remains as difficult of
explanation as before. But the principal obstacle to the acceptance of this hypothe-
sis is that the presence of polar globules in the fertilized eggs of Arthropoda and Ro-
tifera has not been satisfactorily established in a single instance, (compare, however,
the statements made above concerning polar globules in Crustacea, ) much less shown
to be an event of common occurrence. There can be no urgent reason for claiming
that there is an omission or suppression of an event not yet shown to have an
existence.
556 BULLETIN OF THE
So far as has yet been ascertained, this peculiarity has no present
importance, and I know of nothing which affords the least ground for
anticipating such a discovery. |
_ Several observers have raised the question what may be its historic
meaning. Rabl’s theory of a ccenogenetic origin has been already con-
sidered. From a comparison with studies on conjugation among Infu-
soria, Biitschli has arrived at the conclusion that the globule has a
palingenetic signification. The formation of polar globules is a part of
the process of fecundation, and is equivalent to the elimination (mutual
interchange) of “nucleoli” in the temporary conjugation of Infusoria,
and the increasing evidence of their universal occurrence renders such
an (historically) early origin the more probable. Certain objections to
this interpretation, partly anticipated by Biitschli, have been empha-
sized by Whitman, who, besides, finds evidence of the reasonableness of
another theory in the “absence of such cells (equivalents of polar glob-
ules) among the Infusoria.” It may be said in addition, that the cell
nature of the polar globule, being now definitely settled, precludes that
strict comparison of its substance with the “secondary nucleus” of
Infusoria to which a purely nuclear composition (as at first claimed by
Biitschli) would have presented no obstacle.
The opinion, first defended by Strasburger, that the polar globules
have their counterparts in the “canal cells” of plants, opened the way
for the theory (compare p. 463) which Whitman has ably advocated.
The polar globules are a relic of the primitive or asexual mode of repro-
duction. A gamic cell-generation is followed by a line of agamic gener-
ations, the last of which are the polar globules.
This is the only view which offers the least explanation of the fact
that these globules are cells. I believe it forms an important step
toward the solution of their meaning ; but it does not explain why this
agamic process of cell-proliferation reappears after a long period of quiet
growth on the part of the ovum. ‘The signification which most naturally
suggests itself in this connection is that they are representatives of once
functionally active ova; that the renewed proliferation was formerly a
means of increasing the number of the reproductive parts, just as in the
formation of the spermatozoa the mother cells, after a period of growth,
finally break up into a number of individual elements. In the case of
the male elements natural selection has operated, through the multiplied
chances of their failing of the opportunity to execute their normal func-
tion, for the preservation of the functional integrity of every individual,
and even for a great increase in the number of the elements which
MUSEUM OF COMPARATIVE ZOOLOGY. 557
arise by this last act of proliferation. In the case of the ova different in-
fluences have been in operation. The vzgor of the elements has here —i. e.
as compared with the male elements — been a more important factor in
the preservation of the individual and the ultimate success of the race
than the multiplication of numbers. The last act of proliferation has
therefore never resulted, in this case, in the production of more than a
very few individual elements, and these have practically been still fur-
ther reduced by the suppression of the function of the cells called polar
globules, in order to afford the remaining cell (ovum) that increased
chance of survival which a better equipment is capable of insuring.
If this view is tenable, the polar globules are rud¢mentary structures,
and, as such, would be likely to present the peculiarities of such parts.*
There is, in fact, a considerable variation in the size of the globules in
the same species, and a more conspicuous variability in the promptness
with which the reconstruction of the lateral zones of fibre thickenings
into nuclei is effected. Accepting Strasburger’s conclusions as to the
equivalency of polar globules and the “canal cells” in plants, the
“ Bauchkanalzelle ” of cryptogams may perhaps afford even a more
obvious instance of variability in size.
The most important recommendation which this view possesses is the
explanation it offers of the morphological condition of the polar glob-
ules. It would also serve to explain the signification of the peculiar
phenomena observed by Whitman to accompany the production of the
globules in Clepsine. The formation of an equatorial constriction might
then be viewed in the light of an atavistic tendency on the part of the
cell to divide in the original manner into two ova of equal size, and the
gradual, orderly shifting of the constriction as a rapid recapitulation of
changes slowly realized in the history of the race.f
* “Rudimentary organs are very liable to vary in development and in other re-
spects in the individuals of the same species. Moreover, in closely allied species,
the degree to which the same organ has been reduced occasionally differs much.” —
Darwin, Origin of Species, (5th edit., London, 1869,) p. 538.
+t P.S.—The cases of the penetration of a spermatozoén into a polar cell, re-
ported by Fol (79, p. 246), possibly afford further evidence that these cells are
aborted ova.
558 BULLETIN OF THE
Aue HNUD IT X..
Or the numerous papers bearing on the topics here considered which have
come to hand too late to be reviewed in their proper connection, I shall give
an account of only those of Fol, Mayzel, and Pérez ;— those of the two last-
mentioned authors, because they are based upon the observation of animals
very nearly related to Limax campestris; that of the first, because present-
ing features of general interest, as well as many theoretical considerations
concerning matters which I have discussed.
Mayzet’s (’79) paper is a brief notice of the nuclear metamorphosis during
segmentation as observed in the case of nematodes and Limax variegatus. His
observations were first made public at a session of the Warsaw Medical Society,
Nov. 26, 1878.*
The author undertook these observations primarily with the object of ascer-
taining whether Auerbach’s view of a karyolysis or Brandt’s theory of an ame-
bord nuclear division best explained the phenomena. He therefore selected
for study Ascaris nigrovenosa and Strongylus auricularis. It is only as acces-
sory evidence that Limax is introduced, and there is no attempt made to pre-
sent a connected history of the early stages of its development.
The best success was reached by the use of acetic acid, and of the nematodes
Strongylus proved to be the more favorable for study by this process. Mayzel
succeeded in demonstrating in the nematodes mentioned the existence of the
typical fibrous Kernspindel, with granular equatorial Kernplatte, and fibrous
rays around the poles of the spindle. The presence of a small spindle located
at the periphery warrants the inference that the elimination of a polar globule
is preceded by the formation of a maturation spindle.
In Limax the author also found the spindle, nuclear plate, and astral figures,
which accompany the first cleavage. The spindle consisted of very numerous
closely packed, smooth filaments ; the nuclear plate was composed of highly
refractive granules of unequal size ; the astral figure, of fibres very similar to
those of the spindle.+ I can corroborate for the species I have studied the de-
scription he has given, but insist upon the ultimate development of a more prom-
inent distinction between the spindle fibres and the stellar rays than he seems
to have observed. These differences in the condition of the spindle fibres may
* See Mayzel ’79%, 79, and °79°.
t ‘‘Ebenso sind die sonnenformigen Figuren an den Polen der Kernspindel aus
aiisserst zahlreichen, glatten und somit den Spindelfasern ganz thnlichen, gleichfalls
sicher wahrzunehmenden Faserchen zusammengesetzt, bestehen mithin nicht aus in
Reihen angeordneten Kornchen; letztere fiillen zwar die Zwischenraiume zwischen den
Fasern aus, lassen sich aber durch Druck auf das Deckglischen leicht herauspressen.”
MUSEUM OF COMPARATIVE ZOOLOGY. 559
possibly be accounted for by the more or less advanced condition of the spindle
formation. The same differences in the degree of advancement may also ex-
plain why Mayzel did not meet with the nuclear plate composed of granules of
a more uniform size. The conditions he has described I have also seen ; but I
have besides that seen other conditions which do not warrant the conclusion
that the spindle fibres remain like the astral rays, even though they may still
be called smooth filaments.
There is one point especially in which my own observations have not the
clearness I should desire. I have not been able to remove all doubt about the
confluence of the lateral zones of fibre thickenings into a homogeneous nucleus.
It has been difficult to exclude the possibility that in some cases the granulations
may persist to form the nucleoli. Unfortunately, the observations of Mayzel
do not serve to make the matter any more certain. He says: “ Die aus 10-15
Kleinen, hellen ovalen und rundlichen kernihnlichen Gebilden bestehenden
‘Kernhaufen,’ welche ich im Sinne Biitschli’s als zusammenfliessende deuten
mochte, erscheinen bei der Isolation wie von emer gemzinschaftlichen Membran
umgeben.” Iam unable to reach an entirely satisfactory conclusion as to the
nature of the bodies thus described by Mayzel. If, as the author thinks,
they are identical with Bitschli’s “cluster of nuclei,” the signification of the sur-
rounding membrane is not apparent. Bitschli has described no such structure,
and each of his “ Kernchen,” moreover, contains one or more nucleolar bodies.
These Mayzel does not mention, and I have never seen in Limax anything cor-
responding to this condition. It therefore appears more probable that the de-
scription given by Mayzel relates to a subsequent stage, — to one at least as late
as that shown in Fig. 93,— and that his nuclear bodies are really nucleolv.
But the homogeneous condition of the nucleus, if it exists at all, precedes this
stage. Itis certainly an objection to the view I have suggested that the author
looks.upon these nucleus-like structures as in process of fusion. That cannot
be claimed, I think, for the 8-10 small structures shown in Fig. 93, since my
preparations show a constant increase in their number accompanying the in-
crease in the size of the nucleus. I find, then, no sufficient grounds in May-
zel’s observations for changing the opinion previously expressed, that the
thickenings of the lateral zones fuse into a single homogeneous nucleus at an
early stage, namely, before the differentiation of nucleoli.
The researches of Pérez (’79) on presegmentation stages in Helix aspera
possess the merit of covering the very early conditions of the egg,— the
changes which transpire while it is still in the “diverticulum” and the ovi-
duct, —- but the general conclusions at which he arrives do not appear to me
to offer so satisfactory an explanation of the phenomena as the more generally
received opinion.*
* Pérez alludes to the eggs of Limax agrestis, simply to call attention to the fact
that when immersed in water the shell becomes distended by the accumulation of
water between it and the membrane of the albumen. This, he says, may perhaps
explain why Van Beneden held that there was a special liquid between these two
layers.
560 ; BULLETIN OF THE
He has summarized his own results nearly as follows : —
1. The first sign of evolution seen in the mature egg just arrived in the
diverticulum, where it is fecundated, is a peculiar cloudiness of the germina-
tive spot and the appearance of two small “ nucléoles ” in it.
2. The spot becomes diffluent, and difficult to perceive. The germinative
vesicle tends to dissolution.
3. In the protoplasm of the nearly or entirely vanished vesicle there ap-
pears a double star resulting from the liberation of the two “ nucléoles” from
the disintegrated spot. The first system of radiations is thus established.
4, Meanwhile protoplasmic expansions arise from the surface of the yolk.
It is not easy to comprehend their import. After a time, they re-enter the
vitellus.
5. The rays extend and promptly reach the limits of the clear space left by
the vanished vesicle, and invade more or less the vitelline mass itself.
6. There always exist at the centres of radiation small nuclei (noyaux), —
the enlarged “nucléoles” of the germinative spot.
7. When these nuclei have attained a certain size and a vesicular wall, their
vital energy, as well as the attraction which they exert on the surrounding pro-
toplasm, diminishes.
8. The radiate substance then loses its consistency, becomes more fluid, and.
is expelled in two successive drops by the pressure of the surrounding vitellus.
Thus the two polar globules are formed.
9. Neither the stars nor the spindle as such take a direct part in the forma-
tion of the polar globules.
10. These bodies elevate at the surface of the yolk a fine membrane, thus
demonstrating that a vitelline membrane exists.
11. After the formation of the polar globules the double system of radia-
tions is no longer present; the two nuclei previously located at their centres
le in the yolk destitute of “aureola.” Their volume has increased.
12. Since these nuclei have the same origin, directly from the germinative
spot, one of them cannot be considered as a spermatic nucleus.
13. The two nuclei continue to grow, and their “nucléoles” subdivide by
an irregular cleavage until reduced to a multitude of fine granules.
14. The conjugation of the two nuclei is far from being demonstrated.
15. It is more probable that one of the two is totally destroyed, and that the
other persists as vitelline nucleus, to give rise to two “ nucléoles,” which be-
come the centres of a new radial system embracing the whole extent of the
vitelline mass, and determining the segmentation.
It will be seen that, although basing our conclusions on the study of very
nearly related mollusks, we are in agreement in few particulars. This may in
part be explained, I think, by the fact that Pérez seems to have made very
limited use of reagents, especially in certain stages.
As I have not traced the origin of the first archiamphiaster, it will perhaps
appear out of place for me to offer any criticism of the account given by
Pérez. If, however, it be granted that the stars of the first segmentation am-
MUSEUM OF COMPARATIVE ZOOLOGY. 561
phiaster arise in substantially the same manner, —a thing which no one will
be inclined to question, and which Pérez has himself assumed (pp. 392, 393) to
be true, — then the observations on Limax have an important bearing on the
point in question. I have shown that the stars arise not only outside the nu-
cleoli, but even outside the nuclei, at a time when there is no evidence of an
interruption in the continuity of the nuclear membrane. It is therefore impos-
sible to ascribe the stars to the attractive influence of any morphologically
distinguishable portion of nucleus or nucleolus. If any part of the substance
previously contained in the nucleus occupies the centre of the stars, it must
have suffered changes entirely incompatible with the retention of its morpho-
logical integrity.
My confidence in the real equivalency of the astral phenomena throughout
the animal kingdom is too strong to allow the belief that the eggs of Helix
differ in such essential matters from those of Limax. I am therefore compelled
to seek an explanation of the author’s observations which shall be less at vari-
ance with evidence drawn from the study of other animals.
He says that there always exist at the centres of the radiations small nuclei,
the grown-up nucleoli of the germinative spot. His own observations and fig-
ures, however, do not warrant the assertion.* Of the three figures (Figs, 16, 17,
22) which he gives of amphiasters only one shows any central corpuscle, and
only one of the asters of that amphiaster is thus furnished. Figs. 15 and 18,
in which such structures are shown, are capable of a very different interpre-
tation from that given by Pérez. But that is of less importance than to know
whether these corpuscles are derived directly from the germinative spot. I
therefore give the substance of the author’s more extended account of the meta-
morphosis. ‘ La vésicule [tache ?| germinative, d’abord uniformément brillante
(Fig. 6), perd son homogénéité ; elle se trouble, sans pourtant cesser d’étre
claire, par la production de granulations pales et mal limitées (Fig. 7). Au
milieu de ces granulations, on distingue ordinairement assez bien deux petits
nucléoles, que les réactifs rendent plus évidents. Ce sont la les premiers
signes de désorganisation de la tache.” (p. 364.) Subsequently, as though
undergoing dissolution, it becomes pale, and is recognized with difficulty.
Meanwhile the germinative vesicle loses its sharp contour, its membrane be-
comes folded, and an instant later has entirely disappeared. Then there remains
only the protoplasm which it contained and the remnants of the disintegrated
* When he speaks (p. 395) as though it were a matter of surprise that these cor-
puscles had not been recognized as existing in all cases at the centres of the asters,
one is not quite certain what can be meant. They, certainly have long since been
seen, and have been recognized as occupying the centres of the asters. To cite a
single case, Flemming (’75, pp. 120, 191, Taf. III. Fig. 2) has shown that they exist in
Anodonta, and has moreover called attention to their deportment under the influence
of reagents. He has also stated that they are not constantly present. So far as I
can judge, Pérez has not always found them, and my own observations seem to cor-
roborate the fact of their inconstancy. He has seen these corpuscles in the egg be-
fore treatment with reagents. I have not been so successful.
VOL. VI. —No. 12. 36
562 BULLETIN OF THE
*
“spot.” The vitelline granules invade more or less this fluid substance, and
thus diminish the size of the clear space. ‘“ Presque aussitét se manifeste dans
cet espace un systeme radiaire, .... qui consiste en un corps fusiforme aux ex-
trémités duquel se voient deux soleils. Comment cette formation a-t-elle pris
naissance ? Pas plus que les auteurs qui m’ont précédé, je n’ai vu naitre sous
mes yeux ce systeme de radiations.” Notwithstanding a careful study of fresh
eggs in which the germinative spot was in a state of dissolution, no conclusion
was reached by Pérez, except that this stage is of short duration. Acetic
acid, however, has sometimes shown in the germinative vesicle on the point
of dissolution a pale and ill-defined double sun in the midst of irregular frag-
ments coming from the spot (Fig. 8). “A slight pressure easily destroys this
system, which I have never seen displayed in eggs whose germinative spot, less
disintegrated, still allowed one to see its two nucleoli.”
It is clear from the foregoing that the supposed identity of the two
“nucléoles ’ with the corpuscles of the asters rests entirely on the negative
evidence that the “nucléoles ” were not to be seen after the appearance of the
stars. It is not even shown that the corpuscles exist at the centres of the stars
in the early stage represented in his Fig. 8 ; and there is nothing in this figure,
unless it be the nearness of the two stars to each other, which is in the least
inconsistent with their having originated outside the nucleus (germinative vesi-—
cle) ; for the outline of the latter is no longer visible, and the clear space
shown is not of necessity due exclusively to the substance of the vesicle. But
Pérez says further, that as long as the “nucléoles” are distinguishable in the
spot, reagents only render them still more evident. When the spot becomes
confused, however, either the reagents do not cause any definite form to appear
(attributable to the fact that the objects are extremely fragile), or a double sun
is seen. Less satisfactory evidence of a direct continuity could hardly have
been presented. Confessedly there exists a stage in which, both before and
after treatment with reagents, no definite structure is discernible. How, then,
can it be possible for the “nucléoles”’ to persist as central corpuscles in the
stars ?
Pérez seems to have been equally unfortunate in tracing the further history
of these corpuscles. He has often observed in the unaltered egg, either at the
centre of one (Fig. 16) or of both suns, a very small nuclear body very slightly
refringent, and surrounded at a little distance by a vesicular wall, —a body
having, in a word, all the characters of a very young cellular element (p. 371),
and he subsequently (p. 372) says distinctly that it is possible to obtain all
the transitions from the condition presented in Fig. 16 (compare Fig. 48, aa’,
of Limax) to the elements which are subsequently seen at the two extremities
of the spindle ; but unfortunately he has not figured such intermediate stages.
It is true that Figs. 15 and 18 are intended to show such intermediate condi-
tions, but these I believe to be figures of a much later stage than is supposed
by Pérez. He says (p. 400) that Fig. 15 is from an egg which had not yet
produced the first polar globule. In that I think the author may be in error.
He has said at p. 363: “ On peut trouver dans le diverticule d’une Heélice des
MUSEUM OF COMPARATIVE ZOOLOGY. 563
ceufs génétiquement plus agés que des ceufs qui, chez une autre, sont arrivés
dans loviducte, et déja revétus d’albumen. Il y a méme plus: des cufs
venant d’étre pondus n’ont quelquefois pas atteint encore la phase de 1|’émis-
sion des globules polaires, alors que, chez d’autres Hélices, ces corpuscules
s’observent déja dans des ceufs occupant le quatrieme ou cinquieme rang dans
le haut de Voviducte.” All the phenomena which we have hitherto studied
(i. e. up to the formation of the polar globules) may be observed, he says
(p. 375), “in the egg contained in the diverticulum”; and a little farther on
he adds, that Figs. 15 and 18 have been furnished by an egg from the oviduct.
In view of the great variability thus described by him it certainly would
not be impossible that an egg taken, as this was, from the oviduct, should have
already produced the two ale globules. I have not the least doubt that that
is what has transpired in the present instance, and consequently that the
author has overlooked the existence of previously formed polar cells. If it
were permitted from his descriptions to suppose that Fig. 18 was not from the
same egg as Fig. 15, then the latter might possibly represent the first archi-
amphiaster, —a stage antecedent to the formation of polar globules; but in
his explanations of the plates (see also p. 372) he describes Fig. 18 as “ ce qui
reste du corps radiaire de la figure 15, quand on a dégagé par de légers coups
sur la lamelle la majeure partie de la substance qui cache les noyaux.” Still
the difference in the relative sizes of the nucleolar bodies in the two figures
may possibly be taken as evidence that they were not drawn from the same
ego, and that the author only intends in his “ Explanations”’ to convey the idea
that Figs. 15 and 18 are drawn from eggs of the same degree of advancement.
However it may be with Fig. 15, Fig. 18 represents not the vesicular remnants
of two astral figures, but the two pronuclei already closely approximated. It
is more reasonable to suppose that Pérez has in this case overlooked the exist-
ence of the polar globules (a thing which may very naturally happen, since
they are easily detached) than that all observers before him have overlooked
the presence of a large vesicular structure embracing the central portion of
each aster. He asserts that “such is the transparency of the two ‘cellules,’
when sufficiently young, that, owing to the vitelline granulations which indi-
cate their shapes by enveloping them on all sides, one often divines them
rather than sees their contours.” (p. 373.) I think it must be that they are
“divined” in all cases where the examination is made before the formation of
the polar globules. He says himself that eee are much more easily shown
before than after that event (p. 381).
He recognizes the existence of a spindle, but considers it of little impor-
tance. The equatorial enlargements of its fibres are not prominent, although
sufficiently evident in most cases. They consist of a gradual thickening of the
rays up to the equator, or of nodosities distributed along the rays at the middle
third of the spindle. They never appear under the form of a nuclear plate,
an organ, says Pérez, to which is attached a great importance, since it is con-
sidered as destined to give rise to the nuclei which are subsequently seen at
the extremities of the spindle, and, when the latter has ceased to exist, in its
564 BULLETIN OF THE
place. As stated above, these nuclei have, in his opinion, an entirely different
origin. The signification of the enlargements remains to be discovered, but
they do not appear to him to be in all cases essential. Concerning received
opinions about the formation, division, and migration of the nuclear plates, and
their conversion into nuclei, he says: “Cette interprétation n’est nullement
conforme aux faits observés par moi chez |’Helix, et que je viens d’exposer.
Sans nier d’une manicre absolute cette marche des radiations [?] du fuseau vers
les sommets de ce corps, bien que je n’aie rien observé de semblable, je dois
déclarer qwil n’existe pas véritablement de plaque nucléaire chez l’Hélice.
Existat-elle Vailleurs chez cet animal, on ne saurait lui attribuer la production
des noyaux du systeme radiaire, dont lorigine est toute autre, ainsi que je
crois l’avoir démontré.”
Pérez thinks Auerbach, Biitschli, and Strasburger are wrong in making the
nuclei arise in the spindle, and not at the centres of the asters, and explains
as the cause of their error that they have not witnessed the origin of these
structures. When the nuclei are advanced in age, the dynamic influence which
they exert on the surrounding protoplasm ceases, and they then move a little
toward the equator. Manipulation and reagents may also cause or exaggerate
this peculiarity. These, then, are the sources of error into which he thinks
previous observers have fallen !
The mistakes of Pérez already pointed out, and his failure to discover the
nuclear plate, are, I believe, chargeable with all this subversion of the real order
of events, and to the same account must be attributed his misconception of the
nature of the polar globules. I need not repeat the proof, which is entirely in-
contestable, of the cellular nature of these globules, and will only state briefly
the position defended by the author. These globules are formed just as de-
cribed by Robin, with the exception that the second is produced like the first,
and is not, as Robin maintained, already formed before elimination. There is
nothing in Pérez’s description or figures of this stage which is not to be seen in
the living egg. It is, then, not surprising that the globules are considered as
only two drops of the disintegrated radial substance which once surrounded
the “stellar nuclei,” and that neither the spindle nor the half of it escapes as
such from the yolk. It is not sufficient that he tells us he has “ followed at-
tentively the phenomena,” and _ has “ endeavored to discover that which these
savants have described.” There is no evidence that he has used im these stages
the means necessary for the discovery of the things they have described, and it is
therefore to no purpose that the assertion is made, “ Leur structure n’a rien de
V’élément cellulaire, et ils ne naissent point comme lui.” He has “ been able
to recognize neither the spindle nor the two suns between the production of
the first polar globule and that of the second.” “It appears that with this
mollusk there does not remain in the vitellus a single trace of radiate proto-
plasm after the emergence of the two polar globules.” The figures which I
have given for Limax show how probable it is that Pérez has overlooked some
of the stages in the formation of polar globules in Helix.
In his opinion, the radiate substance surrounding the vesicular nuclei having
ee = ee Lee ee
MUSEUM OF COMPARATIVE ZOOLOGY. 565
been eliminated as two polar globules, there are left in the yolk these two nu-
clei. They may, I think, unhesitatingly be considered the “ pronuclei.” He
seems never to have observed them at any great distance apart, although “ some-
times one sees them separated a little from each other, sometimes closely ap-
proximated.” Each. contains a single nucleolus. The nuclei grow. Their
nucleoli undergo a series of irregular segmentations. These divisions do not
seem to have been directly followed, but are inferred from the frequency with
which one finds biscuit-shaped or constricted corpuscles. Pérez is unable to
say what becomes of the two nuclei. He concludes there is no other alter-
native : either one of the nuclei disappears, the other alone being called upon
to inherit the individuality of the ovule, and to assume the dignity of vitelline
nucleus, or the two nuclei fuse. He has not seen the nuclei mutually approach,
but has always found them at some distance from each other, never in imme-
diate contact. For this reason, and on account of a theoretical consideration, —
namely, that the amphiaster immediately preceding the first cleavage is the
same as the first amphiaster, and must, like it and all later amphiasters, arise
from a single nucleus, — Pérez is of the opinion that only one survives and fur-
nishes a lineage, while the other perishes.
He has arrived at the conclusion that there is a genetic connection between
the germinative dot and all subsequent generations of vitelline nuclei, but he
has done so by the introduction of two fundamental errors ; for the corpuscles
at the centres of the asters are not derived, as he claims, from the germinative
dot, nor do they, on the other hand, constitute the nuclei of succeeding gen-
erations.
The mistake concerning the origin of the two nuclear structures (pronuclei)
to be found after the formation of the polar globules, deprives of its impor-
tance his negative statements relative to the penetration of spermatozoa. It
may be, or it may not, that “fecundation is simply the result of the dissolu-
tion of the spermatozo6n at the surface of the vitellus and of the absorption of
its substance by the ovule.” Reasoning from the analogy of cases easier of
control and observation, it is highly probable that in Helix a penetration of the
spermatazoon takes place. Nothing which Pérez has presented in the way of
observation diminishes the probability that such is the case, nor that one of
the nuclei he has seen is the equivalent of the male pronucleus.
Concerning the existence of a vitelline membrane, I think it is quite hazard-
ous to speak dogmatically. It is rarely that I have seen in Limax evidence
(Fig. 57, compare also Figs. 80°, 80°) of the existence of anything resembling
such a membrane. That, however, does not prevent its constant occurrence
in the case of Helix. I am led to suspect, however, by the statement that it
is easily ruptured, that the author may have assumed that it previously existed
in some cases where he had no direct evidence of its presence. At least, his
Fig. 19 shows no trace of such a membrane.
Pérez has contributed very interesting observations on the nature of the egg
just before the formation of the polar globules. No one, I believe, has seen
such strongly marked and numerous pseudopodal protrusions of the vitellus of
566 BULLETIN OF THE
any pulmonate mollusk as he has shown in Figs. 4 and 5. These irregularly
conical, pointed projections of hyaline protoplasm may sometimes attain two
fifths the length of the radius of the yolk, and the larger ones exhibit prolonga-
tions of the granular vitelline substance for a little distance into the central
portion of their bases. They are normally radial in position, but are easily
distorted by manipulation of the egg. The only motion which he has recog-
nized has been a slight displacement of the granules mentioned, doubtless
caused, he thinks, by unobserved changes in the form of the cones.. These
persist for a comparatively long time ; but they are at length contracted into
knoblike processes with narrow pedicels, and then entirely disappear.. “Their
presence coincides with that of the system of radiations which succeeds the
germinative vesicle, and they are always retracted within the yolk before the
escape of the first polar globule.” They recall that which Fol has named
the “céne d’exsudation” in the egg of Asterias. “ But I am able to affirm
that, with Helix, there never exists between these hyaline cones and sperma-
tozoa the relations which this savant has attributed to them in the case of
the echinoderms.”
The pseudopodia which were seen in Limax (Fig. 95) were limited to the
region of the animal pole, were much lower and more rounded, and occurred
at a later stage, than those seen by Pérez in Helix.
For’s (79) finely illustrated memoir on “ Fecundation,” etc., besides con-
sidering more fully than any of his preliminary papers the events of matura-
tion and fecundation, contains extensive bibliographical abstracts and criticisms,
a chapter on segmentation, and the discussion of several topics of theoretical
interest. ?
The author’s observations were made on representatives of echinoderms (As-
terias, Sphzrechinus, Toxopneustes), worms (Sagitta), and mollusks (Ptero-
trachea).
In Asterias the germinative vesicle, “ nucléus de l’ovule,” is composed of a
liquid portion surrounded by a viscid, semi-fluid limiting layer, which does
not merit the name of membrane, in the ordinary sense of the word. Hard-
ened in alcohol or one of numerous acids, the liquid part of the nucleus of a
mature ovarian ovule is surrounded by a membrane presenting a double con-
tour. This does not warrant the conclusion that a membrane exists in the
living egg, but only that the vesicle is limited by a layer which coagulates
differently from the surrounding vitelline substance. The discussion as to
whether this layer belongs to nucleus or vitellus is useless. It is only to be
determined by tracing its origin. This is difficult in the germinative vesicle,
but not in the female pronucleus. The latter is formed —both its con-
tents and its limiting envelope—in the midst and at the expense of the vi-
tellus. “Nucleus” embraces both the envelope and the contents. The fluid
contents are traversed by a network of sarcodic filaments uniting two layers
of like substance, one of which lines the envelope within, while the other
surrounds the germinative dot. The filaments hold in suspension pale, sparse
granules of variable magnitudes. With the use of reagents a greater number
MUSEUM OF COMPARATIVE ZOOLOGY. 567
of them are distinguishable. When the germinative vesicle is about to dis-
appear, the network is no longer to be found, even after employing reagents.
This is proof that it is not an artificial product. The germinative dot is highly
refringent, embraces one or several vacuoles, but no granulations, and is not
surrounded by any layer different from the rest of its substance.
It will be unnecessary to give the details of the metamorphosis of the ger-
minative vesicle and dot, which have been briefly reviewed elsewhere (p. 436).
I will only mention some points of particular interest.
With the flattening of the space (lacuna) which represents the disappearing
vesicle, the substance of the dot changes form, and becomes pale. In some cases
the granular substance of the yolk was seen to encroach upon the “ lacuna,”
especially on the side nearest the surface of the ovule, and to unite with the
remnant of the germinative spot ; in other cases the remnant approached the
periphery of the lacuna, but without penetrating into the vitellus, and some-
times its position appeared to follow no law. The results from hardened eggs
were conflicting as to the connection of the nucleolus with the forming amphi-
aster. In some cases the bipolar rays, emerging from an aster lying outside the
lacuna, abut upon a cluster of granules which are the disintegrated germinative
spot ; occasionally a remnant of the spot is joined by a refringent filament to
one of the asters of an amphiaster; more frequently the fragments of the nu-
cleolus are widely scattered, and then one is certain that there is only a single
aster, though subsequently the amphiaster is seen occupying a nearly horizon-
tal position, and those few fragments of the nucleolus which remain visible are
distant from it. The former cases would indicate that a minimum portion of
the nucleolus contributes to form the amphiaster; the last, that they have no
connection. ‘The author ‘‘ therefore prefers to consider the participation of the
germinative spot in the formation of the ‘amphiaster de rebut’ as improbable,
but without venturing to deny it absolutely.”
Respecting the metamorphosis of the membrane of the germinative vesicle,
he is unable to assert that it is entire, because of the folds which appear
when treated with acids; but whether entire or not, it always forms the
limit between the clear substance and the granular vitelline substance; it
does not expel its contents, as Van Beneden erroneously thought. Whether the
equatorial zone of fibre thickenings in the first spindle arises from the nucle-
olus or from the membrane, is left undecided.
The author still holds to the probability that the amphiaster first formed is
not the “ amphiaster de rebut.” This opinion seems to rest on the oblique or
horizontal position of the amphiaster seen in the earlier stages, as compared with
the radial position observed later, and especially on certain preparations made
with osmic acid, in which an oval corpuscle, embracing vacuoles and having a
denticulate border, occupies the place of the horizontal amphiaster. This he
thinks probably indicates a period of inactivity, during which the amphiaster,
without ceasing to exist, masses itself together. I am not certain how this is
to be harmonized with the subsequent statement that this corpuscle is probably
only an amphiaster little accentuated and disfigured by the osmic acid. Both
568 BULLETIN OF THE
explanations are not necessary. It appears to me that the one last stated is
the more probable, and that consequently there is no ground for doubting the
identity of the first amphiaster formed and that from the external half of which
the first polar globule arises.
The eggs of Asterias are in some particulars less favorable for showing the
manner in which the polar globule is formed, than are those of Limax. Nev-
ertheless the results correspond very closely. From the greater size of the
aster in Limax it has been possible to note more exactly the changes in the
course of its rays as the amphiaster approaches the surface of the vitellus.
Similar conditions doubtless prevail in Asterias ; for Fol says the external
aster (when the protuberance appears) is only a half-aster, since its centre
touches the summit of the protuberance. (Compare his Pl. II. Fig. 10.)
The internal half of the amphiaster, says Fol, alone remains in the yolk ; the
external half constitutes the protuberance, in which one still often sees rem-
nants of the bipolar rays. At other times the external half of the amphiaster
(spindle) promptly disappears, and is resolved into irregular corpuscles. These
remnants are, to judge from the figures, the fibre thickenings of the external
zone, which in the one case remain more regularly arranged; in the other, less
so. The internal half of the aster, continues the author, preserves its structure
intact, and an elongated enlargement is seen upon each of the bipolar filaments.
The detachment of this protuberance to form the polar globule, he thinks,
differs in several important pacticulars from the corresponding changes in seg-
mentation. Some of these differences are the same as those to which I have
already called attention in the case of Limax ; others I believe to be of less
general importance. “ Nous ne voyons pas le globule s’arrondir au point de
ne toucher le vitellus que par une surface extreémement petite, et s’affaisser, une
fois la division opérée, comme c’est le cas dans le fractionnement ordinaire.
Le globule reste accolé au vitellus par une surface relativement large et la
séparation n’a lieu que tres-lentement, par un processus presque impossible a
observer directement.” This appears to me principally dependent on the
presence of the “ Ooléme pellucide,” which envelops the ovum. It is rarely
that anything of a similar nature is observable in Limax (Fig. 57), where there
is nothing to interfere with the free course of the division. In the second
place, says Fol, the rays of the amphiaster (spindle) cut in two do not im-
mediately withdraw toward the centres of their respective asters to contribute
to the formation of the nuclei of two new cells. Those which belong to the
polar globule persist a long time distinct, and the varicosities remain some time
after the division is accomplished. Subsequently there are seen in the globule
granules and vacuoles, irregular both in form and arrangement. A long time
after the formation of the globule these parts are so arranged as to form a rela-
tively large nucleus surrounded with a layer of sarcode. It is unnecessary to
dwell on the significance of these peculiarities ; they are the same as in Li-
max. The re-formation of the fibre thickenings into a nucleus does not occur
with the same rapidity in all cases; but in Limax it may occur almost as.
promptly in the second polar globule (Fig. 60. rn.) as in the formation of the
MUSEUM OF COMPARATIVE ZOOLOGY. 569
female pronucleus. On another point our conclusions are less in agreement.
Fol says the half of the amphiaster remaining in the vitellus contracts and
passes through a short period of repose. Its arrangement remains the same as
during the formation of the first polar globule, but it momentarily fades a
little. It becomes more distinct when the work of expulsion recommences ;
the bipolar filaments elongate, the aster becomes larger, more marked, and far-
ther removed from the surface. The elongated bipolar filaments form again a
fusiform body, the interior extremity of which corresponds to the centre of
the aster, while the exterior extremity is found at the surface of the vitellus.
This external point of convergence is not yet surrounded with rays; but uni-
polar rays soon appear around it, so that exactly the same figure is produced as
at the formation of the first polar globule. The exterior aster of the second
amphiaster almost always lies at one side of the point of contact of the vitellus
with the first globule, and the axis of the amphiaster is usually oblique. His
positive assertions that the internal half of the amphiaster is not massed into
a nucleus, but is transformed directly into a new amphiaster, makes me some-
what distrustful of the conclusions I have expressed on this point; it is at
least of some significance that the granulations at the internal ends of the
spindles in my Figs. 22, 25, 40, are less conspicuous than the corresponding
thickenings in the polar globules. I, however, still believe this feature deserv-
ing of renewed investigation. Fol believes the peculiar position of the centre
of the external aster at the apex of the elevation is explained by the nature of
its physiological réle expressed in the name, sphérules de rebut.
I can confirm for Limax (Fig. 80°) what the author thinks probable in As-
terias, namely, that the envelope of the polar globule is continuous with that
of the vitellus, rather than that the latter is pierced by the forming globule,
although I have not found the envelope especially thin at the summit of the
polar cell (Figs. 22, 25, 40, 61-63).
During the constriction of the peduncle of the polar globule in Asterias, Fol
has observed, as ¢id O. Hertwig, the existence of folds in the vitelline envelope,
radiating from the peduncle on all sides, and most prominent near its base.
This he believes indicates the presence of a superficial layer more inert, less
living than the protoplasm which it surrounds, but not the existence of a veri-
table membrane; a membrane, however elastic it may be, finally becomes
detached from the yolk, and assumes its former position. This it does instantly
under the influence of acids. But here the so-called membrane follows the
division of the protoplasm, and forms an envelope around each of the segments,
never resuming its former position, even if one employs acids before the di-
vision is effected. The same conclusions appear equally applicable to Limax,
although in some cases (Fig. 80°) it may be difficult to assert that the envelope
has not reached a degree of differentiation which closely approaches that of a
genuine membrane. I have only once seen anything like radiating folds at the
surface of the segments, and then (Fig. 68) they were confined to the polar
globule.
Of the formation of the female pronucleus in Asterias, the author says that
5'70 BULLETIN OF THE
the various rays of the aster which remains in the yolk after the elimination
of the second polar globule are amassed and disappear as such; but their
reunited substance, especially that of the bipolar filaments, forms a small cor-
puscle, transparent and difficult to see in the living egg, but very apparent
when treated with osmic acid and carmine. It is at first immovable, and in-
creases gradually in volume; afterwards it moves from the surface, at first
slowly, and then more rapidly. At the side of this arise other pale spots, which,
at first very small, grow rapidly, approach the first one, following its centripetal
movement, and finally fuse with it. The impression conveyed by this deserip-
tion is that only the first pale spot arises directly from the spindle fibres. ‘The
others are not constant in their position. Treatment with acids causes these
spots to appear like nuclei, and one distinguishes a very irregular enveloping
layer ; the smaller the nucleus, the thicker the layer. Within these small nuclei
are one or several nucleoli, which grow at the same time as the nucleus. They
are surrounded with rays which increase rapidly in extent during the growth
of the nuclei, but disappear when the pronucleus becomes stationary. If this
account of the origin of the female pronucleus is accurate for Asterias, there
must be an important difference between it and Limax, for in the latter I am
very sure there are no accessory nuclear vacuoles which are entirely indepen-
dent of the spindle fibres.
He says these changes transpire the same, whether the eggs have been fecun-
dated or not, except in regard to the position of the polar globules (inside or
outside the vitelline membrane) ; but they occur a litle more rapidly when the
eggs have been fertilized.
The maturation of the eggs of the sea-urchin offers little additional informa-
tion. The amphiaster and the single polar globule are larger in proportion to
the size of the egg than in Asterias, and once two rows of granules (zones of
fibre thickenings) were seen, one near each pole of the globule.
The germinative spot is wanting in the very young as well as in the maturer
egos of a Sagitta, which the author names S. Gegenbauri. There are other
species of this genus in which the nucleolus is present. The office filled by
the nucleolus in the development of the ovule, the author therefore concludes,
cannot be one of primary importance. The place of the large germinative
vesicle, which has grown smaller and disappeared, is occupied, before the exclu-
sion of the egg, by a compact corpuscle with stellate borders, in the interior of
which is to be distinguished, after treatment with very weak solutions of osmic
acid and bichromate of potash, a vertical row of small refringent grains, the
optical section of the plane which the granules constitute. This phase resembles
that one which in Asterias was the cause of the author’s denying the identity
of the first amphiaster and that from which the first polar globule arises. The
two globules are produced successively, and in fecundated eggs are restrained
by the vitelline membrane, being forced into a depression which they cause in
the surface of the yolk, but in non-fecundated eggs they are detached, and
are retained only by the mucilaginous envelope. Here also these changes all
transpire more slowly in eggs that have not been fecundated.
SS ee ee Ae wes >
MUSEUM OF COMPARATIVE ZOOLOGY. safe b
As was to have been expected, the events of maturation in Heteropoda show
a greater resemblance to those in Limax than either of the other groups.
The author withholds judgment as to whether the limiting layer of the ovule
is in this instance a true membrane, since he has not satisfied himself experi-
mentally of its physical and chemical properties. In young ovules it has the
aspect of a membrane, but its internal contour becomes less distinct in those
that are mature. Whether it is resorbed or mingled anew with the vitelline
sarcode, it does not exist after the exclusion of the egg. The nucleus of the
egg at the time of deposit is identical with the nucleus of the ovule (i.e. ger-
minative vesicle). It then appears in the living egg as a clear spot at the
centre of the yolk, which soon vanishes, and the central part of the vitellus
then assumes a more homogeneous aspect, in which, however, a radial figure is
discernible. In about half an hour there appears on one side of the yolk a
clear space resting with a broad base at the surface, and continuing toward the
centre in the form of a cone. It is composed of protoplasm without any
“protolecith.” As it increases in size, the lecithic globules, especially near the
surface, take on a radial arrangement about the centre of the clear space. In
an hour and a half the protuberance of thé first polar globule appears, and
within it one can distinguish the bipolar filaments and their enlargements
without the use of reagents. Two hours and three quarters after exclusion
the first globule is entirely detached, and the radial arrangement of the
“lecith” indicates the formation of the second amphiaster; at this moment
there appears a voluminous protuberance at the nutritive pole, composed of
protolecith and sarcode. The superficial layer of the latter is here thicker
than over the other parts of the yolk. At the end of three and a half hours
the second giobule is fully detached, and the vitelline protuberance has mean-
time entirely disappeared. Prolongations often seen arising from the surface
of this protuberance (Pl. VIII. Fig. 9) are trabecule resulting from the retrac-
tion of the albumen of the coagulated egg, and therefore do not pertain to the
vitellus.* Fol is unable to give any explanation of the meaning of this pro-
tuberance. — The metamorphosis of the germinative vesicle as shown by hard-
ened eggs confirms in many ways the views at which I had arrived. The
vesicle at the time of exclusion is still quite distinct, provided with a limiting
layer, and embraces a network of sarcodic filaments, but contains only a
few irregular refringent granules in place of a nucleolus. The enveloping
layer, the so-called membrane of the vesicle, becomes less distinct, although it
still remains visible. The vesicle diminishes a little in volume, but preserves
an almost spherical form, without shrivelling. At the opposite poles of this
great rounded cavity one now distinguishes two masses of granular substance,
* It should be remarked in this connection, however, that the author subsequently
(page 112) alludes to this as a protuberance ‘‘ with its accumulation of protoplasm
and sometimes pseudopods at its surface (Pl. VIII. Fig. 9, Ev').” Since this is
the same figure as that cited in connection with the description given above, it would
appear that the author may have changed his opinion concerning these pointed ele-
vations between the times of the two writings.
572 BULLETIN OF THE
in texture exactly like that which surrounds the vesicle and stretches out
between the globules of “protolecith.” “ These masses protrude slightly into the
cavity of the germinative vesicle, which otherwise remains perfectly rounded.” *
This internal limitation is therefore very easy to distinguish, but externally they
are absolutely indistinguishable from the vitelline sarcode of which they form
apart. From these masses stria soon arise which take the direction of me-
ridional lines. These become more distinct, and are changed into [?] veritable
filaments. Falling short of the equatorial plane, they do not yet encounter
each other. During all the phases of their formation, the peripheral extremities
of these filaments are in continurty with the protoplasmic network which occupies
the interior of the nucleus. As the rays advance, the network disappears. It is
more than probable that the rays are only a modification of the form of the
intranuclear network, and that they result from a regular arrangement of
its trabecule. This view of the origin of the spindle fibres is not directly
reconcilable with the one I have expressed; nevertheless, I see no occasion
to modify the argument based on the great distance which in Limax inter-
venes between the nucleus and the centres of the asters. The account of the
origin of the polar masses I will give in the words of the author.
“ Quant aux amas polaires, leur origine premiere est bien plus difficile a établir.
J’avoue que, pour ma part, je n’y suis pas parvenu et qu’a cet égard je ne puis
que poser une alternative sans la résoudre. Ces amas peuvent provenir du
sarcode intranucléaire qui se porterait aux deux pdles opposés du noyau et se
confondrait avec le protoplasme vitellin, ou bien ils peuvent provenir du proto-
plasme périnucléaire qui ferait irruption dans la cavité de la vésicule ; 4 moins
encore que ces deux processus ne se produisent simultanément, et qu'il n’y ait,
dés le premier instant, une fusion entre ces deux substances. Que cette fusion
soit immédiate ou non, il est incontestable que les protoplasmes intra- et péri-
nucléaire ne tardent pas 4 se confondre aux deux pdles, en sorte que, un peu
plus t6t, un peu plus tard, il y a toujours fusion.
“Tes amas polaires faisaient d’abord une légere saillie dans l’intérieur de la
vésicule sphérique. Pendant la croissance des rayons intranucléaires, ils s’éloi-
gnent du centre et font de part et d’autre hernie dans le vitellus. Il en résulte
que la vésicule passe de la forme sphérique @ celle dun citron trés-court. Pen-
dant ce temps les rayons nucléaires, qui se trouvent pres de Paxe qui rejoint les
deux pdles, sont arrivés & se rencontrer et se sont sondés de manieére a consti-
tuer quelques filaments bipolaires; les rayons latéraux de chaque aster vont
encore se perdre dans le réseau intranucléaire.” )
The extranuclear rays arise at the same time as the intranuclear, and the
growth of both is exactly alike. There is therefore a time during which each
centre of attraction is surrounded by a system of rays without being yet joined
to that of the neighboring aster. The amphiaster occupies at first an eccen-
tric position. The small grains representing the nucleolus may possibly go
directly to the spindle, since granules of entirely similar appearance are seen
along the intranuclear rays when the amphiaster is still incomplete. The
* Not italicized in the original.
MUSEUM OF COMPARATIVE ZOOLOGY. 573
author, however, doubts the genetic connection, since these granules are often
entirely wanting. Subsequently the amphiaster is completed by the welding
of the intranuclear rays end to end, and the “granules de Bitschli” make
their appearance as enlargements of the bipolar filaments. But the relation of
these enlargements to the grains presented by the still isolated rays remained
obscure. The amphiaster elongates, and at the same time stretches the mem-
brane of the vesicle. The vitelline rays have increased in extent, and the
centre of each aster is occupied by a few granulations, around which is a space
occupied by homogeneous protoplasm. Meanwhile the membrane of the ger-
minative vesicle assumes indefinite contours and entirely disappears. The
amphiaster moves toward the periphery; at first oblique, it becomes perpen-
dicular to the surface, with which the centre of one of the asters becomes
almost “flush.” Then the surface is raised into a dome, and the enlarge-
ments of the bipolar rays divide ; the first polar globule, composed of half the
“amphiaster de rebut,” is detached. The internal half undergoes the same
modifications as in Asterias, but the second amphiaster is smaller than the
first. Portions of the bipolar filaments and their enlargements are readily dis-
tinguished at, and some time after, the formation of the globule. The enlarge-
ments all lie at the same height ; at the time of segmentation the polar globule
has assumed the appearance of a cell with a large nucleus, and one or several
nucleoli. They decompose, and have no part in the development of the egg.
The views of the author, it will be observed, seem to have been modified in
some particulars since the publication of his earlier paper on Heteropoda. See
pp- 429, 430.
The principal events of fecundation as described for Asterias have already (pp.
480, 486) been given. It is necessary to add only a few particulars. The “ cone
of attraction” may extend to half the thickness of the mucilaginous layer
if the spermatozoon advances slowly, but is much shorter and more rounded
when it approaches quickly, for as soon as the contact between the two is
effected, the cone commences to retract. Most spermatozoa enter the nutritive
hemisphere, but one often sees a penetration in the formative half, even up to
the immediate vicinity of the polar globules. At the moment when a space
appears under the vitelline membrane around the point of fecundation, the
differentiation, but not the elevation, of the membrane has extended quite
around the vitellus. From this instant the egg is inaccessible to every sper-
matozoon which reaches the membrane; for the vitellus is no longer able to
produce a “céne d’attraction,” and in Asterias a spermatozodn is hardly
capable of penetrating without the aid of this excrescence. The space embraced
between the elevated membrane and the yolk is occupied by a transparent sub-
stance, which cannot be a liquid, but must be a very clear jelly, since, if it were
a liquid, the vitellus would change position, and the space could not remain of
uniform thickness all around. Does this substance arise exclusively as a secre-
tion from the yolk, or is there at the same time an imbibition through the
vitelline membrane? If the former, the vitellus should suffer a diminution ot
volume. It is difficult to determine whether this is so, on account of the
574 BULLETIN OF THE
changes in the form of the yolk. If the latter diminishes in volume, it can be
but little. The vitellus and membrane have a greater diameter than existed
before the formation of the membrane. The author therefore speaks of an
elevation of the latter, and not of a retraction, which appears to him doubtful.
The orifice through the membrane at the “crater” which gave exit to the
“cone of attraction,” and possibly existed during the early stages of the forma-
tion of the “cone of exudation,” is no longer to be found after the complete
dispersion of the latter cone, nor is the crater longer visible. Directly under-
neath this “crater” of the membrane there is a corresponding but smaller
depression in the surface of the yolk. This is still visible when the membrane
is wholly elevated, but before the male pronucleus is formed. The latter
appears as a small clear spot without granules immediately under the vitelline
crater.
The phenomena occurring in the sea-urchin have been considered at page 490.
The vitelline membrane is elevated with greater rapidity and energy than in
the case of Asterias. The zodsperm suffers little change of form at penetra-
tion. It enters progressively by the action of the vitelline sarcode, and is not
impelled by its cue, which has ceased its undulatory movements. The “cone
of exudation” is extremely pale and very mobile. The author does not know
whether this is a phenomenon of amceboid contractions or a continuous erup-
tion of an almost liquid substance. The body of the spermatozodn once
plunged into the yolk is often visible without the aid of reagents. The point
of penetration is only determinable by the fact that the female pronucleus
retires only part way from the formative pole toward the centre of the yolk.
With this as a criterion it may be shown that the penetration takes place at
any point, but perhaps more often in the nutritive hemisphere.
The growth and union of the pronuclei is nearly the same in starfish and
sea-urchin. In Asterias the clear spot where the zodsperm penetrated becomes
the point of departure for the male pronucleus, which at first remains for sev-
eral minutes immovable and without apparent change. The vitelline rays are
all directed toward the centre of the spot ; some of them are slightly curved
so as to abut at the point of the surface where the cone of exudation still per-
sists. The rays become longer and more accentuated with the advance of the
aster into the yolk. Its direction, at first centripetal, changes when the female
pronucleus does not occupy the centre of the egg, so as to encounter the lat-
ter. If the egg is fecundated before the completion of the polar globules, the
male pronucleus remains at. the edge of the yolk in the condition of a small,
hardly visible spot until they are eliminated. Both pronuclei then arise simul-
taneously. In this case they meet between the centre and the formative pole,
because the male pronucleus advances more rapidly.
In the sea-urchin, while the clear spot is contiguous to the surface, its in-
terior often shows a rounded refringent globule, which appears to correspond
to the body of the spermatozo6n modified in form, and soon becomes in the
living egg invisible. Treatment with osmic acid and carmine shows that the
zoosperm preserves a few instants its conical form, then becomes rounded into
MUSEUM OF COMPARATIVE ZOOLOGY. 575
a strongly colored corpuscle, which is surrounded by a clear area and rays. In
approaching the female pronucleus, the corpuscle increases to nearly double
its original size. Preparations made when the female pronucleus is already
surrounded by rays of the male aster show that the nucleus is almost con-
stantly oval, and drawn to a point on the side nearest the male pronucleus.
The nature of the male pronucleus is especially elucidated in the star-fish.
It is sometimes only as large as that of the sea-urchin, but at other times
twice as large; in the latter case it no longer has a homogeneous appear-
ance, but is surrounded by an enveloping layer which is darker than the
contents. The cause of this difference is unknown, but it establishes a transi-
tion between the condition shown by the sea-urchin and that of the Hetero-
poda where the two pronuclei have the same size and texture. Were it not
for this transition, it would be difficult to ascertain whether the dark cor-
puscle of the sea-urchin corresponds to the pronucleus of the Heteropoda or
only to its nucleolus.
Besides the results already (p. 479) mentioned, the study of the pronu-
clei in Sagitta have afforded other points of particular interest. The altered
form, which I ventured to assume for the male pronucleus, is actually encoun-
tered, and corresponds almost exactly with that of the pronuclei in Limax,
Fig. 68. I extract the following from the author’s description of the changes.
Although fecundated at the moment of deposit, the vitellus shows a male
aster only at the time when the polar globules are formed. It probably exists
already at the edge of the yolk, but it must be quite small, since it escapes
observation. Soon after the elimination of the globules there appears near
the surface of the yolk, usually at the nutritive pole, a round or oval vacuole,
the male pronucleus. The female pronucleus appears almost at the same in-
stant. They move toward the centre, increasing in size, and meet between it
and the formative pole. The female pronucleus is without an aster, that of
the male grows rapidly, and lies in advance of the pronucleus. The cavity of
the male vacuole 1s surrounded by a sharp margin, except at the place where it
touches the centre of the aster. There it appears open, as though the contents of the
cavity passed by gradations into the substance forming the central mass of the aster.
The vacuole always asswmes the form of a melon-seed. This description corre-
sponds in almost every particular with the condition in Limax alluded to above.
The author, believing from the appearance that the pronucleus is drawn on in
a passive condition, and that the agency must be sought in the male aster,
endeavored to show by reagents the presence of the body of a zoésperm, or a
compact corpuscle, in the centre of the aster. Failing in this, “he must con-
sider the vacuole and the central mass of the aster taken together as the homo-
logue of the male pronucleus of other animals.” This conclusion, if extended
to the cited case in Limax, would involve one in the necessity of identifying
the central area of the same aster with both male and female pronucleus ; and
in Sagitta certain stages in the approximation of the pronuclei (op. cit., Taf. X.
Fig. 7) appear to present the same difficulty, for the relation of the female
pronucleus to the aster is at this stage essentially the same as that of the male
576 BULLETIN OF THE
pronucleus. In Sagitta both are “open” on the side toward the centre of the
aster, and in Limax both are drawn out in the same manner, and their out-
lines become less conspicuous on the side toward tne aster. But while Fol
represents the line which indicates the contour of the pronucleus in Sagitta as
terminating rather abruptly, I have simply seen the outline become very
gradually less distinct, but never wholly interrupted. The pronuclei in Limax
present the same smooth, even contour on the side toward the aster as else-
where ; it is only less conspicuous, not less precise, on that side.* There is,
besides, this difference in the two cases : in Sagitta the aster arises in connec-
tion with the male pronucleus, but in Limax in connection with the female.
At this stage (Pl. X. Fig. 7), continues the author, a eorpuscle is generally
seen suspended in the liquid of the cavity of each of the vacuoles, near
the side with which they are about to come in contact. They are very dis-
tinct, owing to the low refractive power of the liquid, and are comparable to
the nucleoli found in the pronuclei of other animals. The pronuclei have
the form of a grape from which the stem has been torn; it is by this trun-
eate side that they approach each other, separated by only a thin layer of
vitelline substance. Some of the rays of the aster now converge toward
the space which separates the two pronuclei, and the others toward the infe-
rior t extremity of the male pronucleus. When the pronuclei meet, the rays
extend around both, converging toward the line which separates them. In
coupling, they are mutually flattened. Fol’s Fig. 10 seems to indicate that
they are no longer “ open” when this flattening begins. They always deport
themselves optically, he continues, like vacuoles full of liquid in the midst
of a denser substance.- The contours are perfectly distinct, but simple and
without indication of a membrane or limiting layer. Variable sarcodic masses
are visible within the pronuclei. The rounded mass (nucleolus) of the pre-
ceding stage has disappeared, and in its place are seen sometimes filaments,
sometimes partitions, at other times streaks of sarcode stretching across the
cavity in various directions, and exhibiting enlargements of all forms and sizes.
The stars of the first cleavage amphiaster evidently arise in Sagitta, also, he-
fore the fusion of the pronuclei ; for the author says that, when considerably
flattened, there often appear at their opposite lateral edges small lenticular
masses which project into their cavity. (Compare loc. cit., Taf. X. Fig. 9.)
The corresponding events in the Heteropoda offer many points of resem-
blance with Limax. In one place the author speaks incidentally of the mul-
tiple condition of the female pronucleus. When it is composed of two or three
small nuclei, each of them, he says, contains its own nucleolus. The figure
* From the difficulty of rendering a sharp outline on stone with the crayon, the
pointed ends of the pronuclei in Fig. 68 are not quite so definite, especially in the
later prints, as they should be.
+ From the figures cited it is evident that the blunt ae of the pronucleus is
meant, although it is wpypermost in the figure. The description may date from a
period before the author began to deviate from the customary method, by placing the
vegetative pole of his figures uppermost.
MUSEUM OF COMPARATIVE ZOOLOGY. 577
cited (PI. I. Fig. 13) is the only one which shows such a condition, and even in
this one of the small nuclei is so covered by the other that the proof of their
independence is not conveyed by the figure alone. If this condition really is
met with, it must be very rare, for the author would otherwise have given a more
detailed account of it. The internal star of the second amphiaster is much less
developed and disappears earlier than in Limax. At its first appearance the male
pronucleus is situated just underneath the surface of the yolk, rarely in the
immediate vicinity of the nutritive pole. though more often in the nutritive
hemisphere. It has no relation with the protuberance at the nutritive pole.
He believes the latter is more accentuated when this pronucleus arises in the
formative hemisphere. Both pronuclei develop with the same rapidity and in
the same manner; each soon presents a large nucleolus in its interior; but the
female pronucleus advances little or not at all toward the centre of the vitellus,
because [?] it is soon joined by the male pronucleus, whose motion is infinitely
more rapid. After treatment with picric or acetic acid the pronuclei are, at
the moment of their appearance, homogeneous. A little later a certain number
of small spherical grains, each of which is furnished with a black point in its
centre, appear in the interior. Still later the pronuclei present the vesicular
character of true nuclei, the limit being formed by an irregular layer of vari-
able thickness. Neither osmic acid nor alcohol causes this layer to appear.
The contents remain clear and transparent after treatment with osmic acid, but
become granular with the other reagents mentioned. The nucleolus is variable
in different eggs. More often there is only a large one in each nucleus, but it
often happens that there are insted several small nucleoli. Since the latter
condition occurs in less advanced stages, it may be that the nucleoli become
fused, or that one is developed to the exclusion of the others. The rays which
surround the male pronucleus during its displacement, and are visible in the
living egg, disappear after the use of reagents. It is possible that the same
may be the case with Limax. Fol has given no figures of this stellate arrange-
ment, but his statement is explicit. The two pronuclei may have attained
their full size at the time of contact, or “they may be still relatively little de-
veloped (Fig. 7), and in the latter case the conjugated nucleus will be obliged to
increase after its formation.” I doubt if this last statement is warranted by the
figure cited. There does not appear to be here, more than with Limax, a veri-
table conjugation nucleus. Unless I misinterpret this figure, it shows already
the beginnings of the amphiaster of segmentation, and there cannot well be a
further growth, but only a metamorphosis of the two pronuclei into a segmen-
tation spindle. The nucleoli, continues Fol, still exist when the pronuclei are
in juxtaposition, but they disappear at the moment when the latter are fused.
During this fusion picric acid still causes the enveloping layer to appear, and,
within, granulations arranged in lines diverging from the point of union.
The results of the fecundation of immature or over-ripe eggs of Asterias, or
such as are taken from animals kept in confinement, all being abnormal, have
been given at pp. 484, 485, 491.
The phenomena of segmentation were most extensively pursued in Toxo-
VOL. VI. — NO. 12. 37
578 BULLETIN OF THE
pneustes. After fecundation the vitellus remains in repose for about twenty
minutes. There is a collection of transparent substance which forms an irregu-
lar layer around the central nucleus. The radiations in the yolk appear before
the nucleus has suffered reduction of volume; they are optically like the sub-
stance which surrounds the nucleus, not like that of the nucleus itself. They
diminish in breadth at the moment the latter is converted into an amphiaster.
Auerbach’s theory is refuted by these facts. Subsequently the nucleus is a
little elongated, and the perinuclear protoplasm takes the form of a disk sur-
rounding the nucleus, as the ring of Saturn does its planet. The disk is oval;
when seen in profile the vitelline rays appear to diverge from it like the barbs
of a feather. Treated with acetic or picric acid, the radial structure, contrary
to the effect produced in subsequent stages, becomes less distinct. This phase
lasts about twenty minutes. The protoplasmic disk meantime gradually dimin-
ishes in breadth and increases in length. Then it promptly becomes limited to
two masses quite distinct from each other. The rays are no longer arranged
like barbs, but like the spokes of a wheel. The nucleus becomes indistinct;
reagents cause it to reappear in the form of a lemon. At the pointed extrem-
ities the limiting layer of the nucleus projects outward, and serves as centres for
the two systems of rays. In acetic acid the latter are seen with great distinct-
ness ; they are without enlargements, and are soon lost in the midst of vitelline
substance of uniform appearance. One or two of the granules in the nucleus
are distinguished by their size and greater refringency, — perhaps a nucleolus in
process of dissolution. Osmic acid confirms the existence of these conditions.
Transitions from this to the next described phase are not often met with in
the sea-urchin, but are more readily found in the heteropods, in connection
with which they are described.
In this next phase the spindle with equatorial fibre thickenings is already
formed. It is during this stage that the second vitelline membrane begins to
be detached. After treatment with picric acid there is no trace of an envelop-
ing layer (membrane) around the nucleus; each aster is composed of distinct
parts: a central, nearly spherical, clear, protoplasmic mass ; a peripheral gran-
ular part, dark especially in the vicinity of the central mass, and of a radial
texture remarkable for its delicacy and regularity. The dark substance termi-
nates abruptly with a regular contour, but is not separated from the central
mass by any membrane or envelope whatever. The limits are less pronounced,
but not wanting, on the side toward the old nucleus. The centre of the clear
portion is occupied by a cluster of granules, toward which all the filaments are
directed. They stop at the edge of the clear mass; it is exceptional to see a few
of the intranuclear filaments send pale prolongations as far as these granules.
Rotation of the egg shows that the spindle is flattened so that its cross-section
is elliptical, and that the cluster of granules at the centre of the aster has the
form of a crescent, and therefore appears in section as a round body of limited
extent. Treated with osmic acid, the extranuclear rays are almost obliterated,
so that the central mass appears with greater distinctness. In acetic acid the
unipolar rays are seen with surprising clearness, and a remnant of the nuclear
MUSEUM OF COMPARATIVE ZOOLOGY. 579
envelope becomes visible. This pseudo-membrane surrounds only the middle
part of the nucleus; it is wanting at the ends. The grain at the middle
of each filament is evidently a simple enlargement of its substance. The
unipolar rays are extremely delicate toward their extremities, and at one
point are much swollen. Unlike those of the interior of the nucleus, — which
are more rounded, distinct, and refringent, and perfectly regular in their
arrangement, — these enlargements are elongated, variable in form, and placed
at irregular distances from the centre of the aster, so that the enlargements of
consecutive filaments never lie adjacent to each other. There may be filaments
with two enlargements, others with none. The effect of staining in gold
chloride appears to be, to a certain extent, an indication that the view I have
expressed about the nature of the spindle fibres at their initiation is erroneous,
Fol observes with this treatment that the asters assume a beautiful dark violet
color, which at the periphery gradually merges into the color of the yolk, which
is of a rose tint. The nucleus and the intranuclear rays, without being de-
stroyed, remain pale, — “‘ are not more stained than the rest of the vitellus.”
The next phase is characterized by the division of the fibre thickenings,
which cannot be observed, however, in the living egg. The vitellus changes
form, now in one direction, now in another, but ultimately elongates in the
direction of the axis of the amphiaster. In picric acid the enlargements, after
division, appear larger and more elongated than in the preceding stage. The
interzonal filaments are very pale, and soon disappear ; they are named “ fila-
ments connectifs.” The flattening of the amphiaster increases, so that the
spindle and areas appear in one position twice as broad as they do after being
rotated 90° about the axis of the spindle. The granules of the “area” (sarco-
dic mass) are also extended in the same plane in the form of a cylindrical bol-
ster, which may be straight or slightly curved. The extranuclear rays form a
compact zone around the “ area,” and appear composed of pieces in juxtaposi-
tion like the bricks in anarch. ‘Toward the exterior these pieces are continuous
with granular rays. This structure is of limited extent, and since it exists at
precisely the time when the rays in the living egg extend to the periphery of
the yolk, it is to be concluded that the rays consist of two distinct parts, of
which one (the central) is brought out by picric acid, while the other (pe-
ripheral) is only seen in living eggs. The author cites two figures (Pl. VII.
Figs. 9, 11) to illustrate the condition shown at this stage after treatment with
acetic acid. The description relates principally to Fig. 11. The nuclear fila-
ments are not distinguishable from those of the vitellus, and the granular
mass at the centre of the aster, not being discernible, is probably veiled by
them ; but the region which extends between the two groups of intranuclear
enlargements * is not thus covered ; one should therefore be able to see the
filaments which connect these enlargements in pairs,t if they exist. It is easy,
* In Fig. 11 no such groups are represented, unless, as the author may possibly
have assumed, they are already fused with the “‘ sarcodic mass” at the astral centres.
t Fig. 9 shows a spindle with equatorial enlargements ; consequently the ‘‘ con-
nective filaments”’ are not to be sought in that stage.
580 BULLETIN OF THE
on the contrary, to be assured of the absence of every connective filament in
this region ; it is occupied by a uniformly granular vitellus. Since acetic
acid has the effect of making all sarcodic filaments so distinct, this fact appears
to the author significant [of what ?]. I think no difficulty can be experienced
in interpreting Fig. 9 ; it is Fig. 11 which still remains to be explained. I be-
lieve it corresponds to my Fig. 82. That the latter does not exhibit a stage
subsequent to the formation of the equatorial plate is evident from a comparison
with Figs. 90-93. I have assumed that it corresponds to a stage preceding the
formation of a veritable spindle. The principal difficulty with this, as with
Fol’s interpretation, is in explaining what has become of the substance which
usually appears at this time in the form of spindle-fibre thickenings. . To
assume, as Fol does, that this substance has already passed through the stages
of division and migration, is in contradiction with every other figure he has
given. Iam not sure that both these cases may not represent abnormal condi-
tions, — either a more complete dissolution and distribution of the substance
of the nucleus than is usual, or a failure of the vitellus to respond as promptly
as usual to the changes in the nucleus. It is perhaps possible that Fol’s Fig. 11
represents a stage nearly corresponding with that of his Fig. 14 (Pl. VIL.), and
that the envelope of the nucleus has simply disappeared a little sooner than
usual. In that event, there might be some reason, even in his observations,
for retaining the view that the spindle fibres are at first composed of vitelline
filaments. But however that may be, further observations are necessary to
render either of these figures (Fig. 11 or Fig. 82) satisfactorily intelligible.
During the next stage the constriction of the yolk begins, and the second
membrane is detached on all sides, although it follows the constriction for a
certain distance. The “grains de Bitschli” reach the sarcodic mass of their
respective asters, at the edge of which they appear as small spherical bodies,
sometimes still arranged in a plane parallel to the equator, sometimes without
order. They vary in size and are hollow. At the opposite margin of each
“area” is another group of much smaller globules. The latter are still abun-
dant, and derived in all probability from the central granular masses of the
asters. Ultimately these two groups are intermingled. This may take place
before the larger globules have become hollow, or not till after they have in
addition each acquired a nucleolus. . ;
The stage which follows ends with the separation of the segmentation spheres.
The asters continue to move apart and pass the centres of their respective
spheres ; the ‘‘areas” have become conical or pyriform. The rays are curved,
as already described by Auerbach. The vitelline membrane has failed to fol-
low the furrow, and stretches across it from one sphere to the other. In picri¢
acid the larger globules of the “area” are increased in size, and each contains a
nucleolus. They are, therefore, true nuclei. The larger they (nuclei) are, the
less their number, from which it is probable that they unite with each other.
Their arrangement is irregular, The rays on the outer side of the “area”
converge toward a point at the external side of the mass ; all the other rays,
toward the centre of the mass. In osmic acid the exterior form of the yolk
MUSEUM OF COMPARATIVE ZOOLOGY. 581
and its membranes is better preserved than in picric acid. The vitellus as a
whole still continues flattened, and the same peculiarity affects the “ areas ”’
and the contained globules. The bodies of the centre of the aster appear small
and homogeneous. At first located in the centre, they subsequently approach
the young nuclei, with which they ultimately unite. Certain pale corpuscles
between the first and second membranes are not polar globules, but result
from a precipitate formed in the albuminous fluid by the reagents. The
descriptions and figures of the corpuscles which occupy the centre of the aster
do not seem to me to afford satisfactory proof of the conclusion, that they are
fused with the new nuclei. Figs. 13, 14, of Fol’s Pl. VI. show thickenings in
the interzonal filaments.
In describing the formation of the polar globules in the Heteropoda, Fol
expresses his belief that all the “matieres de rebut” eliminated from the egg
correspond to a single cellular element. Here, too, the female pronucleus is
formed by a fusion of the central corpuscle of the deep aster with the compact
corpuscle formed at the expense of the “‘renflements de Btitschli.” As he has
seen only one such corpuscle result from the enlargements, he thinks there is
every reason to believe that the supplementary small nuclei (which he finds
here) are formed, as in Asterias, independently of the first pronucleus in the
substance of the central mass of the internal aster.
The first segmentation in the Heteropoda is as follows. The pronuclei be-
come mutually flattened, the enveloping layer disappears from the surface of
contact. This region of contact is the centre of an irregular system of diver-
ging rays extending inside as well as outside the nuclei. This might be
mistaken, he says, for the origin of the amphiaster; but by comparisons
he has convinced himself that these first radial striae correspond only to
the molecular activity which is developed at the moment of the fusion of
the nuclei, and that it disappears before the amphiaster arises. However it
may be with the Heteropoda, I believe it is not thus with Limax. According
to the further description, the plane of union is still visible in Heteropoda
after the stars of the amphiaster have appeared. The latter always fall at
opposite margins of that plane. At other times the fusion is more complete
when the asters arise. 'The pronuclei meanwhile migrate nearly to the centre
of the yolk. The contours of the (conjugated) nucleus remain visible up to the
moment when the intranuclear enlargements are grouped in the vicinity of
the centre of each aster. The middle region of the “filaments connectifs”
(PL IX. Figs. 8, 9, 10, Ft) is composed of fine fibrille, which, the author
states, have been incorrectly engraved, so that they appear like thickenings of
the filaments. The spaces around the centres of the asters are occupied by
granular protoplasm exhibiting a radial structure. Perhaps they correspond,
he says, to the sarcodic masses which occupy the same position in the sea-
urchin, The vitelline filaments of the latter would then correspond to the
radial trails of protoplasm which stretch out between the lecithic globules of
Pterotrachea. In that event equivalents of the rays immediately around the
centre of the aster in the mollusks would not exist in the sea-urchin, or would
be invisible by reason of the homogeneous nature of the sarcodic mass.
582 BULLETIN OF THE
Compared with the first “amphiaster de rebut,” the present amphiaster is
characterized by the absence of vitelline rays, so prominent in the former, and
the presence of this granular mass of protoplasm, which is wanting in the
other. The axis of this amphiaster is curved, with its concavity directed to-
ward the formative pole. It may be that this curvature sustains some relation
to a vitelline protuberance which is at this moment visible at the nutritive
pole. The author is ignorant of the signification of this protuberance, as he
was of that which arises at the formation of the polar globules.
In the following stage the groups of fibre thickenings have approached
closely the central corpuscle of each aster. The protuberance of the nutritive
pole begins to be separated from the vitellus by a circular constriction ; other-
wise the yolk is perfectly rounded, and shows no indication of a segmentation
furrow.
This furrow makes its appearance in the next stage around the vitellus on
all sides ; it passes to one side of the protuberance. Bitschli’s corpuscles unite,
on both sides, into two or three nuclei, which at once become swollen, and
assume the appearance of vesicles, each with an enveloping layer and embra-
cing irregular granules. These vesicles, some or all of them, become elongated
in the direction of the central corpuscle of the aster, and present an opening
like the neck of a bottle, which is extended almost into contact with the cen-
tral corpuscle. The vesicles fuse into a single one, having the same form, thick
walls and a large corpuscle, which is drawn to a point on the side toward the
areal mass. The latter has disappeared, without doubt by absorption into
the nucleus, and the contents of the nucleus are in continuity with the clear
substance at the centre of the aster, at the expense of which the nucleus seems
to grow. While the segmentation is being accomplished and the new nuclei
are growing and taking the place of the asters, the protuberance at the vitelline
pole gradually disappears by fusing with that one of the spheres of which it
formed a part; thus one of the products of segmentation is more voluminous
than the other.
His researches on Sagitta are especially valuable, since made almost exclu-
sively on living eggs. They confirm the results obtained from the study of the
Heteropoda. The first sign of the impending division vs the formation of small
masses of sarcode at the opposite extremities of the nucleus, which is still intact
and spherical. These small masses are optically like the vitelline sarcode, and
cause a slight indentation into the cavity of the nucleus, which, though not
prominent, is still readily appreciable on account of the perfect sphericity of
the rest of the contour. The vitelline rays tend to arrange themselves about
se : ; :
the extremities of the nucleus in place of converging towards its centre. Thus
is quickly produced the dumb-bell stage. The central mass of the asters is
perfectly homogeneous. The intranuclear trail differs from the surrounding
vitellus only by the presence of the connective striz (interzonal filaments),
which are pale and poorly defined. The contents of the new nuclei are clearer
and less refringent than their vicinage. The centre of the aster is often occupied
by a dark corpuscle. In the interior of the nucleus pale, ill-defined streaks of
eee =
MUSEUM OF COMPARATIVE ZOOLOGY. 583
protoplasm are seen, which together resemble the tongue of a bell, and are
joined with the central substance of the aster. During the second and subse-
quent segmentations these streaks of sarcode become at a certain moment much
more distinct than during the first segmentation ; they take special forms,
which recall the stamens of a flower. There are from four to six of them, but
their position is not constant. They attain their greatest distinctness only
when the nuclei are so swollen as to be perfectly spherical. Although a mor-
phological continuity of these trails (trainées) with the enlargements of the bi-
polar filaments appears improbable, it is not absolutely impossible. One might
suppose that only a part of the enlargements serve to form the envelope of the
young nuclei, and that another part persists under its primitive form [the
trails] to become subsequently the intranuclear network. Whatever their ori-
gin, these trails of protoplasm disappear during the growth of the new nuclei,
and contribute without doubt to the formation of the sarcodic network. The
nucleoli make their appearance only a long time after the disappearance of these
trails, so that they do not seem to have any direct relation with them.
The author arrives at the following conclusions concerning the process of
segmentation in general.
The first precursory phenomenon is the appearance of a stellate figure, —
a radial arrangement of the vitellus, of which the nucleus is the centre. At
this moment the nucleus is still intact, but a little less distinct than before ;
this appears to indicate that there are movements, — forces which exert their
influence at the same time upon the nucleus and upon the vitelline protoplasm.
The refringency of the nucleus and the distinctness of its contours are the only
things which are modified, up to the moment when the new centres of attrac-
tion appear at its opposite poles. The nature of these forces are far from being
elucidated, but there are in all cases places where a gradual passage is estab-
lished between the nuclear substance and the vitelline protoplasm ; there are
therefore points of fusion between the two substances. These centres persist a
certain time under the form of corpuscles or of granular masses. The rays of
the amphiaster appear at first in immediate contact with the centres, and then
stretch out in all directions. They fall into two categories, according as they
extend into the interior of the nucleus or into the vitellus. The former are the
only ones that are joined end to end. Both kinds bear enlargements ; but
those of the extranuclear filaments have no other destination than to add their
mass to that of the centre of the aster, while the intranuclear unite in the
vicinity of the centre of each aster into one or a small number of corpuscles,
which become swollen and unite into a single vesicle, and thus become the
origin of the new nuclei. The corpuscles occupying the centre of the star
also contribute to the formation of the nuclear elements, which continue to
grow at the expense of the sarcodic masses of the asters. The “filaments con-
nectifs” remain outside the new nuclei, and do not contribute to their forma-
tion. The new nuclei therefore absorb only a part of the substance ‘of the old
nucleus, and in return are united with substances which formerly constituted
a part of the vitellus. The formation of the polar globules takes place by the
584 BULLETIN OF THE
process of cell division. But the second “amphiaster de rebut” arises directly
from the internal half of the first. One may compare the two polar globules
to a cell originally single.
In the cases of superfecundation the union of two male asters to a female
pronucleus results in a conjugate nucleus, which soon gives place to a tetraster,
in which four equidistant stars occupy the corners of an imaginary square, the
sides of which are formed by the intranuclear filaments. In division each of
the four groups of filaments (spindles) shows a series of enlargements which
divide and migrate as usual. The two groups migrating toward each corner of
the square unite to form a single nucleus, so that from the eight groups there
result only four nuclei, one to each aster. There are many variations from this
more typical condition. Instead of a tetraster there may be a pair of parallel
amphiasters, and according as the corresponding asters of these amphiasters
are more or less intimately joined by their sarcodic rays, the condition of the
tetraster will be more or less closely approached. This is followed by a corre-
sponding segmentation into four spheres, which resemble in position the condi-
tion after the second normal cleavage. So at subsequent stages there are eight
instead of four spherules, etc. In the planula stage the larve are irregular.
The formation of a tetraster, and the division into four spheres at once, the
author thinks, is not simply an abbreviation of events ; it is a more funda-
mental alteration of the normal process.
Where there remain male pronuclei which have not become fused with the
female, (in cases where several spermatozoa have penetrated the yolk,) sooner
or later each of these male pronuclei is resolved into an amphiaster, from which
two nuclei arise. When two or three of the male pronuclei have united with
a corresponding number of the components of the female pronucleus, and there
are others which remain distinct, the conjugated nuclei give rise each to a
tetraster, and the superfluous male pronuclei also divide, but with less regu-
larity. All eggs embracing independent male asters are very irregular in their
seementation. All those which have received more than one spermatozo6n give
rise to at least twice as many segmentation spheres as would exist in a normal
embryo of the same stage of development, and become monsters. This mon-
strosity consists in the repetition of a primitive organ which should normally
remain single. Other results have already been given at pages 484 and 491.
Fol, rejecting the term “deutoplasm,” introduced by Ed. van Beneden, pro-
poses to distinguish the nutritive substances accumulated in the vitellus from
those often deposited by the embryo in its interior, and to designate the former
as “protolécithe,” the latter as “ deutolécithe.”
‘He proposes further to preserve the term membrane only for the thin layers
with double contour, which are harder and more resistant than the protoplasm,
and which have lost the ability of remingling themselves directly as living
substance with the living protoplasm. He would class under the name of
limiting or plastic layers (couches limitantes or plastiques) those which have the
peculiarity of following the sarcode in all its changes of form, even the most
extreme, and of re-entering directly into the protoplasmic circulation, together
Se st eee eee
MUSEUM OF COMPARATIVE ZOOLOGY. 585
with those which the protoplasm can easily and instantaneously traverse with-
out being first obliged to dissolve them. Limiting layers, which have only a
single clear contour, while the other surface passes by insensible transitions
into the neighboring substance, may be given the name of “ pellicule.”
Fol has also been impressed by the fact, that in the formation of the polar
globules the centre of the external aster reaches the surface of the vitellus, and
subsequently continues to occupy the most external portion of the globule until
the latter is almost detached. Without having observed the curvature of the
rays, he remarks that*the aster is of necessity incomplete, and thinks these
peculiarities should correspond to a difference (from ordinary cell division) in
the mechanism and forces of division. The amphiaster is in some way expelled,
pushed by a vis a tergo, instead of operating as two “centres @appel.” Since
they subserve no function for vitellus or embryo, and soon suffer disintegration,
he prefers the term globules or spherules to that of cells. Granting that there
are objections to the use of “globules excrétés,” he claims the justice of the
name “corpuscules de rebut.” They are small masses of a substance that has
become superfluous, or rather injurious, to the egg, and are for that reason
expelled. It is of little significance that this substance has, as germinative
vesicle and dot, played an important part in the growth of the ovule, or
that its mode of expulsion resembles the division of cells ; they are none the
less worn-out materials, and their constancy in the animal kingdom simply
tends to show that these substances have become injurious, —an obstacle to
“la fécondation intime” and to embryonic development. From all observa-
tions it appears that the expulsion of a part of the nucleus of the ovule may be
a condition indispensable to the fusion of the pronuclei. If that is the case,
one is naturally led to inquire if there are not in the germinative vesicle sub-
stances of different affinities or polarities. The combination of these would
give a totality which would have no affinity, no attraction, for the male ele-
ment. In fact, the zodsperms do not advance toward the interior of the
vesicle so long as the latter remains intact. The eliminated substances should,
by this hypothesis, have a polarity of the same name as that of the zodsperm,
or the same chemical affinities. One could then understand how it is that the
presence of a zodsperm in the vitellus hastens the elimination of the polar
globules. On the other hand, the penetration of a zodsperm into a polar
globule —a fact which has been once or twice observed — would remain inex-
plicable. The cause of the obstacle which it seems to offer to fecundation
would be seen in its size and inactivity. The expelled portion would be the
more passive, the female pronucleus the more active principle.
Even if in fecundation it is evident that a zodsperm exercises an influence
upon the vitellus from which it is still separated by a relatively large space, the
mechanism of that action is not clear. The author sees only three hypotheses
which can accord with the facts. The zodsperm may be separated only in ap-
pearance ; there may be a continuity of sarcodic substance as soon as the
action is exerted. But. as he has found no filament of sarcode extending from
the zodsperm toward the vitellus, and no change in the form of the body of
586 BULLETIN OF THE
the former, such as must result if such a filament exists, it only remains to
assume pre-existing filaments which arise from the surface of the vitellus.
These might, a priori, be represented as extremely delicate filaments traversing
the odlema in radial lines; but as they have never been discovered in the
hardened or living egg, it is necessary to deny their existence. The second
hypothesis is that the action of the vitellus is in response to a pressure exerted
" by the zodsperm upon the intervening portion of the striate envelope through
which it endeavors to advance. As the vitellus does not react upon the press-
ure of all kinds of bodies, it is necessary to admit that there is some peculiar-
ity, — some special rhythm arising from the undulations of its cue. But it is
difficult to understand how this pressure could be appreciated through half the
_thickness of the odlema, or communicated to a definite extent of the vitelline
surface, or why the cone of attraction should arise exactly opposite the most
advanced zodsperm. ‘The last supposition consists in admitting an attraction,
the nature of which is unknown, which exercises an influence not only by im-
mediate contact, but also at a slight distance ; although this hypothesis itself
needs to be explained. The composition of the cone of attraction is not better
understood. Is it a substance secreted by the vitellus, or a prolongation of the
vitelline sarcode, and, in the latter case, is it an accumulation of the superficial -
limiting layer, or of the deeper layer? The first hypothesis is excluded, in the
author’s opinion, by the case where the protuberance is of considerable volume,
and the continuity of its substance with the vitelline sarcode is evident, but
between the other two hypotheses he remains undecided. The cone of exu-
dation, on the other hand, is only a liquid, slightly refringent substance,
without cohesion, which is ejected or excreted by the surface of the yolk.
Fol distinguishes three kinds of centres of attraction, — the male, the female,
and those which preside at segmentation. The male centre takes its origin in
a spermatozoon,* whose “ body” becomes the centre of an aster and the point of
departure in the formation of the male pronucleus. I am not certain what
he means by that part of the statement which I have italicized, since he has
shown more clearly than any one else that the male aster does not always
centre at the middle of the male pronucleus. I can reconcile this statement
with the fact mentioned only by assuming, either that he thinks the male pro-
nucleus is formed eccentrically to the head of the spermatozoon, or that this
statement is only intended to be an approximate expression of facts. The
former assumption is the less probable, because he adds : “ It is important not
to forget that the body of the spermatozoén is no longer intact at the moment
when these phenomena (astral) appear; it has changed form and has in-
creased in size by the absorption of vitelline sarcode.” I therefore think the
* The author thinks recent observations tend to-show that the spermatozoon is
formed of cellular protoplasm, to the exclusion of the substance of the nucleus. Conse-
quently the male pronucleus is formed by the union of two protoplasms, which have
not suffered a single admixture of the substance of preformed nuclei. ‘‘ Le pronu-
cléus male ne descend & acun titre, pas méme en partie, d’un noyau plus ancien ; il
est de formation nouvelle.”
MUSEUM OF COMPARATIVE ZOOLOGY. 587
author has attached far too little importance to his observations on Sagitta
(Pl. X. Fig. 6). He remarks that the attraction is therefore exercised not so
much by a simple spermatozo6on as by a fusion of this with the sarcode, and
that it is this union which gives rise to the male pronucleus. This statement
approaches so closely the view I have already advocated, that I should be in-
clined to think our ideas on this point identical, were it not that he sub-
sequently explains his position in a manner which shows clearly that in his
opinion it is the substance of the male pronucleus which exercises the attractive
influence rather than a force liberated in the act of the union. He says, sub-
stantially : “ The male center is surrounded soon after its formation by a star
of unipolar rays. Shortly the centre, represented by the body of the more or
less modified spermatozo6n, is surrounded with clear protoplasm. This mass
continues to increase, —a fact which seems to indicate that the sarcodic rays
are the expression of centripetal currents of protoplasm coming from the vitel-
lus. However that may be, it is certain that the aster is formed around a
modified spermatozoén which is found at its centre ; that it is a result of the
action exercised by this corpuscle upon the surrounding vitellus. If this is so, it
should be explained why the evidence of this attraction ceases when the
nucleus has attained its maximum size.
The phenomena of attraction, Fol continues, are perhaps less striking for
the female than for the male pronucleus, but they exist none the less. They
are, —(1.) radial lines, which continue to augment in proportion as the pro-
nucleus absorbs vitelline sarcode, and are only effaced at the moment when it
has come to rest ; (2.) the centripetal advance of sarcodic currents, of which the
radial strize are the visible expression, and the direction of which is indicated
by the growth of the nucleus ; (3.) the displacement of the pronucleus itself
from the periphery toward the centre of the yolk.
The centres of attraction which appear at the poles of the amphiaster of
segmentation are due to a fusion (rencontre et alliage) of nuclear substance
with vitelline sarcode at the circumscribed points (poles) where the contour
of the elongated nucleus becomes lost. But this is not the first process pre-
liminary to the formation of the amphiaster. On the contrary, in the case
of the sea-urchin the appearance of a mass of sarcode around the nucleus,
as well as the “pinnate figure,” precedes. The latter appears to be the
expression of centrifugal rather than centripetal currents; the formation of
typical asters, on the other hand, only dates from the moment when the nuclear
and vitelline substances enter into communication at the poles of the nucleus.
The three cases have in common this point: that the phenomena of attraction
(and of repulsion) may precede the mingling of two diverse substances, but that
they attain their full development, and interpret themselves by the formation
of a veritable aster, only when there has been a fusion of the two substances ;
the point of fusion is then always the centre of the system of rays. It seems
to me this last statement is more in harmony with the view I have maintained
than it is with the ideas which Fol has himself previously advocated. In my -
opinion it is the point of fusion, and not necessarily the product of the fusion,
588 BULLETIN OF THE
which marks the centre-of attraction ; it is the force set free in the act of fu-
sion, not the affinity of the already formed nucleus for other matter, which
induces the radiate appearance. If this view is justified, it seems to me that
it would not be necessary to make a special case of Sagitta,.and to hesitate,
as Fol does (p. 259), in comparing the structure which he there calls by the
non-committal name “la vacuole” with the male pronucleus of other animals.*
I have less hesitation in pronouncing this “vacuole” in every essential the
equivalent of the male pronucleus of other animals, as I have seen something
so nearly identical in Limax (see Fig. 68), where the staining of the structure
in question banishes all doubt as to its nuclear character. I must confess,
moreover, that I am considerably puzzled to know what Fol means by this
hesitancy, as I see no other possible explanation in view of the ultimate fate
of this vacuole. Instead of presenting any difference of primary, or even sec-
ondary importance, it seems to me a very welcome confirmation of the substan-
tial identity of the astral phenomena which accompany the male pronucleus
and those which preside at the subsequent segmentations.f
In regard to the nature of the rays, the author says, the hypothesis of a
simple polar attraction which arranges the vitelline granulations in a certain
order without displacing them is not defensible ; for these bands are in all
cases broader than the mean distance of the lecithic granules. These fila-
ments, so distinct in acetic acid, do not admit the belief in a simple polari-
zation of molecules. The accumulation of clear protoplasm around the nucleus
and its poles could not take place without currents of this viscid substance,
But if there are currents, in what direction are they produced? In the sea-
urchin, before the formation of the amphiaster, the perinuclear mass moves
toward the equator, and becomes a disk at the moment when the pinnate
arrangement of the clear streaks becomes visible. Here it may well be that
the currents arising in the equatorial region proceed beyond the poles to spread
their substance in the vitellus. During the division of the amphiaster the
facts appear to favor the supposition of centripetal currents.. The centripetal
movement of the thickenings [in the unipolar rays] which are rendered visible
by acetic acid, and the continuous growth of the central masses, appear to indi-
cate a slow advance of the sarcode toward the centre of the aster.
Nevertheless, observations on other objects must, he says, be taken into the
account. Auerbach’s theory of a dispersion of nuclear fluid is untenable, since
the asters are formed before the volume of the nucleus is diminished. On the
other hand, Flemming has seen pseudopodia at the surface of the polar globule
in Anodonta, of which the following explanation is offered. From the figures
J
* “‘Chez Sagitta, par exemple, nous avons vu que l’aster traine a sa suite une
sorte de vacuole toujours croissante ; le centre de l’aster se trouve au bord allongé de
cette vacuole, toujours du cdté vers lequel elle se dirige. C’est done dans l’aster et
dans son centre que réside la force motrice, tandis que la vacuole, que j’hésite du
reste 4 comparer au pronucléus des autres animaux, est trainée a sa suite.”
t P. S. — May it not be that this is a typographical error, and that the negative
has been inadvertently omitted ?
MUSEUM OF COMPARATIVE ZOOLOGY. 589
(Flemming’s) it is to be seen that the polar globule is half formed at this time,
and consequently “ Biitschli’s corpuscles” are already divided. As is known,
the external aster is incomplete, its centre having arrived at the surface and
being only partly surrounded by unipolar filaments. It is therefore natural to
presume, he says, that the pseudopods correspond to unipolar filaments, which
are wanting in consequence of the superficial position of the aster. If this rea-
soning is correct, he adds, this is a case where the filaments are elongated in a
centrifugal direction during a part of the period of division, to be subsequently
retracted. If the pseudopodia belonged to a somewhat ae phase, I should
think there would be greater justice in this conclusion. The position of the
rays after the division of the equatorial zone, as shown in Limax, Fig. 50, does
not seem easily reconcilable with Fol’s interpretation.
But the observations of Strasburger on Spyrogyra also tend, continues the
author, to establish the existence of centrifugal currents during the division
of the amphiaster. If, now, we compare the unipolar filaments with these
pseudopodal filaments (Spirogyra), the former should be considered as streaks
of sarcode stretching out toward the periphery, but having the opposite course
after the division of the intranuclear enlargements.
The changes within the nucleus are also instructive. The formation of the
- spindle from the intranuclear network and the division and migration of the
fibre thickenings appear to result from an action exercised upon the interior of
the nucleus by two centres placed at its poles. It is not possible to say what
the nature of this action is. An internal repulsion would not explain the
eccentric position of the “amphiaster de rebut.” A simple attraction would
not explain the formation of Biitschli’s corpuscles. On the other hand, the last
part of the act of division, the formation of new nuclei, appears explainable
upon the hypothesis of an attraction exerted by the centres upon their vici-
nage, and of the mutual repulsion of the asters. A central attractive influence
on the part of the new nuclei would explain the process of segmentation, ex-
cept in the case of the polar globules.
The evidences of the existence of repulsions are the progressive separation of
the poles of the amphiaster and the mutual repulsion of the male asters. After
the female pronucleus has been superfecundated the conjugated nucleus and the
independent male asters are all situated at the external third of vitelline rays.
This regularity of situation indicates that they occupy a position of equilibrium
between opposing forces, and these forces can only be an attraction toward
the centre of the yolk on the one hand, and a mutual repulsion on the other.
The attraction between the sexual nuclei is a special case in which this force
is very evident. The motion of the male aster is correlated with the position
of the female pronucleus; it has not a constant relation with the vitellus.
In the further development, the rhale elements exercise a preponderating
influence, as the existence of the tetraster after fusion with more than one
zoosperm shows; the isolated male asters pass through the stages of amphi-
astral division, but the isolated (unfecundated) female pronucleus decomposes
without exhibiting any of these changes.
590 BULLETIN OF THE
The male pronucleus arises when a living zoésperm penetrates into a mature
and living vitellus. In certain cases (sea-urchin) it is not much larger than
the “body” of a zodsperm, and one might then entertain the opinion that it is
only sucha “body” swollen. It then forms the centre of an aster. In other
cases (Heteropoda) it becomes as large as the female pronucleus, and is not sur-
rounded by a radial figure.* This growth is not a simple inflation of the body
of a zodsperm by a liquid, because when fully developed it contains many
times the original quantity of protoplasmic substance ; it is not a process of
nutrition, a digestion of vitelline substance, since that physiological process is
complicated and requires a considerable time for its accomplishment, while the
absorption of vitelline substance is direct and prompt. The male pronucleus
is therefore a product of the union of spermatic protoplasm with vitelline pro-
toplasm, and from this fusion results a nuclear body possessing a multitude of
properties which are wanting to the isolated zojsperm.
Likewise the female pronucleus, which has its first origin in the “ corpuscules
de Biitschli” belonging to the internal half of the second “ amphiaster de rebut,”
is derived for the greater part from vitelline sarcode. The disproportion be-
tween nuclear and vitelline substances in this case is fully as great as between
the body of the zodsperm and the completed male pronucleus in the Hetero-
poda.
Finally, the cleavage nuclei are formed at the expense of the “central
masses” and of the intranuclear varicosities of the old nucleus. These “masses”
may also descend, in part at least, from the old nucleus. But even here the
substance derived from that source is only a fraction of the whole mass of the
new nuclei. Besides, a part of the substance of the old nucleus remains en
route under the form of the “trainée internucléaire,” and does not enter into
the composition of the new cytoblasts.
A consideration of the origin of the nucleus in these three cases leads to the
same conclusion, that its substance comes in part from a pre-existing nucleus or
a foreign element, and in part from the protoplasm of the cell, —the latter by _
way of fusion, not of nutrition. The young nucleus while still quite small
exercises a strong influence on the surrounding vitellus. In proportion as it
increases in size, this influence diminishes, and once completed, it ceases to ex-
ist. It therefore seems permitted to conclude that the attraction or influence
exercised by the young nucleus increases in proportion as it is fused with cell
protoplasm, and subsequently diminishes when the proportion of the latter
element is too great. There would be a period of activity followed by a period
of saturation ; the latter would supervene as soon as the nucleus attained the
limit of its growth.
I can omit a presentation of the author’s “ Théorie électrolytique des Mouve-
ments protoplasmiques,” with which he ‘terminates his paper, since it is not
directly applied to an elucidation of the phenomena under consideration.
* The author has previously stated, I believe, that in the Heteropoda the male
pronucleus is surrounded by rays in the living egg. See p. 577.
MUSEUM OF COMPARATIVE ZOOLOGY. 591
ALPHABETIC LIST OF THE LITERATURE.
Agassiz, Alexander.
64. Embryology of the Starfish. Contrib. Nat. Hist. U. 8S. A., Vol. V. Pt.
1,66 +9 pp., Pl. I-VIIL 1864.
’67*. On the Embryology of Echinoderms. Mem. Amer. Acad. of Arts and
Sciences, n. ser., Vol. IX. Pt. 1, pp. 1-30, 38 cuts. 1867.
'77. North American Starfishes. Mem. Mus. Comp. Zodl., Vol. V. No. 1,
iv + 136 pp., 20 pl. 1877.
Agassiz, Louis.
’'57. Contributions to the Natural History of the United States of America.
(First Monograph, Part III. Embryology of the Turtle.) Vol. IT. pp. 451
— 643, 34 pl. Boston: Little, Brown, & Co. 1857.
’62. Same. (Second Monograph, Parts III.-V.) Vol. IV., viii. + 380 + 12
pp., Pl. XX.-XXXV. (17 pl.). Boston: Little, Brown, & Co. 1862.
Arndt, Rudolf.
’68. Studien iiber die Architektonik der Grosshirnrinde des Menschen. IT.
Arch. f. mik. Anat., Bd. IV. pp. 407 - 526, Taf. XXV., XXVI. 1868.
‘76. Ueber den Zellkern.’ Sitzg. des med. Vereins zu Greifswald. 4 Nov.
1876.
Arnold, Julius. .
'78. Die Abscheidung des indigschwefelsauren Natron im Knorpelgewebe.
Arch. f. path. Anat. u. Physiol., Bd. LXXIII. Heft 1, pp. 125-146,
Taf. II. 8 May, 1878.
Auerbach, Leopold.
'74. Organologische Studien. Zur Characteristik und Lebensgeschichte der
Zellkerne. 262 pp., 4 Taf. Breslau: EH. Morgenstern. 1874.
'76. Zur Lehre von der Vermehrung der Zellkerne. Centralbl. f. d. med.
Wissensch., Jahrg. XIV. No. 1, pp. 1-4. 1 Jan. 1876.
76°. Zelle und Zellkern. Bemerkungen zu Strasburger’s Schrift: ‘“ Ueber
Zellbildung und Zelltheilung.” Cohn’s Beitrage zur Biologie der Pflanzen,
Bd. II. Heft 1, pp. 1-26. 1876.
'77. Ueber die streifige Spindelfigur bei der Vermehrung, resp. Theilung der
Zellkerne. Bericht tber die Miinchener Naturforscherversammlung, 1877.
Abstract in Hofmann u. Schwalbe’s Jahresberichte, etc., Bd. VI. Anat.
Abth., p. 25.
Axmann, C. F.
'47. De gangliorum systematis nervos. structura penitiori ejusque functioni-
bus. Dissert. inaug. 1 pl. Berlin. 1847.
592 BULLETIN OF THE
Baer, Karl Ernst von.
'27. De ovi mammalium et hominis genesi. Epistola ad acad. imper. scient.
Petropol. 8+ 40 pp. Cum tab. aen. et color. Lipsie: L. Voss. 1827.
’35. Untersuchungen tiber die Entwickelungsgeschichte der Fische, nebst
einem Anhange tiber die Schwimmblase. 52 pp., 1 Taf., mehreren
Holzschn. im Texte. Leipzig: Vogel. 1835.
37. Ueber Entwickelungsgeschichte der Thiere. Beobachtung und Reflex-
ion. Zweiter Theil, 315 pp., Tab. LV.-VII. Konigsberg: Gebr. Born-
trager. 1837.
’46. Neue Untersuchungen tiber die Entwickelung der Thiere. Froriep’s
Neue Notizen, Bd. XXXIX. No. 839, pp. 833-40. 1846.
Balbiani, G.
'73. Mémoires sur le Ae voloppament des Aranéides. (Lab. de physiol. au
Mus. d’hist. nat. dirigé par M. Claude-Bernard.) Bibliothéque de, l’école
des hautes études, section des sci. nat., Tom. VII. Art. 6, 91 pp., 15 pl.
Paris. 1873.
Also in Aun. des Sci. nat., 5 sér., Zool., Tom. XVIII. Art. 1, pp. 1-91, PL.
I.-XV. 1873.
"76. Sur Jes phénoménes de la division du noyau cellulaire. Compt. rend.
de PAcad. des Sci., Paris, Tom. LXXXIII. No. 18, pp. 8831-834. 30 ©
Oct. 1876. :
Balfour, Francis M.
'75*. A Comparison of the Early Stages in the Development of Vertebrates.
Quart. Jour. of Mic. Sci., n. ser., Vol. XV. No. 59, pp. 207-226, Pl. X.
July, 1875.
"76. Onthe Development of Elasmobranch Fishes. Jour. of Anat. and Phy-
siol., Vol. X. pp. 877-411, 517-570, 672-688, Pl. XV., XVL, XXI-
XXVI. Jan., Apr., and July, 1876.
‘78. A Monograph on the Development of Elasmobranch Fishes. (Reprint
of '76.) 11+295 pp., 20 pl. and 9 woodeuts.. London: Macmillan
& Co. 1878.
78°. On the Phenomena accompanying the Maturation and Impregnation of
the Ovum. Quart. Jour. of Mic. Sci., n. ser., Vol. XVIII. No. 70, pp.
109 = 131) 17, cuts... Aprs 1375)
"78. On the Structure and Development of the Vertebrate Ovary. Quart.
Jour. of Mic. Sci.,n. ser., Vol. XVIII. No. 72, pp. 883-4388, Pl. XVII.
—-XIX. Oct. 1878.
80. A Treatise on Comparative Embryology. Vol. I., xi + 492 + xxii pp.,
275 figs. London: Macmillan & Co. 1880.
Bambeke, Charles van.
'70. Sur les trous vitellins que présentent les coufs fécondés des Amphibiens.
Bull. de ’Acad. roy. de Belg., 2 sér., Tom. XXX. pp. 58-71, 1 pl. 1870.
'76. Recherches sur l’embryologie des Barware —I. Huf mir non fécondé 5
If. (Euf fécondé. Bull. de Acad. roy. de Belg., 2 sér., Tom. XLI. No.
1, pp. 97-185, 2 pl. 8 Jan. 1876.
MUSEUM OF COMPARATIVE ZOOLOGY. 593
"76°. Recherches sur l’embryologie des poissons osseux. (Présenté 7 Nov.
1874.) Mém. cour. et des savan. étrang. de Acad. roy. de Belg., Tom.
Mais G6 pp., d pl. 1876.
Barrois, Charles.
76. Mémoire sur lembryologie de quelques Eponges de la Manche. Ann.
des Sci. nat., 6 sér., Zool., Tom. ILI. Art. 11, 84 pp. Pl. XIJ.-XVLI.
30 June, 1876.
Beneden, Edouard van.
'70. Recherches sur la composition et la signification de l’ceuf, basées sur
Vétude de son mode de formation et des premiers phénomenes embryon-
naires (mammiféres, oiseaux, crustacés, vers). Prés.] Aug. 1868. Mém.
cour. et des savan. étrang. de Acad. roy. de Belg., Tom. XXXIV. (1867
—70), 283 pp., 12 pl. 1870.
"75. La maturation de l’ceuf, la fécondation, et les premiéres phases du déve-
loppement embryonnaire des mammiféres d’apres des recherches faites chez
Je Lapin. Bull. de l’Acad. roy. de Belg., 2 sér., Tom. XL. No. 12, pp.
686-736. 4 Dec. 1875.
'76*. Contributions 4 l’histoire de la vésicule germinative et du premier
noyau embryonnaire. Bull. de l’Acad. roy. de Belg., 2 sér., Tom. XLI.
No. 1, pp. 88-85, 1 pl. 8 Jan. 1876.
76”. Contributions to the History of the Germinal Vesicle and of the First
Embryonic Nucleus. Quart. Jour. of Mic. Sci., n. ser., Vol. XVI. pp.
dbo — 182, Pl. XIII. . Apr. 1876.
’'76°. Recherches sur les Dicyemides, survivants actuels d’un embranchement
des Mésozoaires. Bull. de lAcad. roy. de Belg., 2 sér., Tom. XLI. No.
6, pp. 1160-1205. 3 June, 1876.
Was eave.» tom. XLII: No.7; pp. 35-97, Pl. 1.—-III. 1 July; 1876.
77. Contribution a lhistoire du développement embryonnaire des Téléosti-
ens. Bull. de Acad. roy. de Belg., 2 sér., Tom. XLIV. No. 12, 31 pp.,
L pl. 1877.
'78. A Contribution to the History of the Embryonic Development of the:
Teleostean Fishes. Quart. Jour. of Mic. Sci., n. ser., Vol. XVIII. No.
69, pp. 41-57, Pl. IV. Jan. 1878.
Beneden, P. J. van.
’40. Recherches sur le développement des Aplysies. Bull. de lAcad. de
Brux., Tom. VII. No. 11, pp. 289-245, 1 pl. 1840.
Also in Etudes embryogéniques. Bruxelles. 1841.
Beneden, P. J. van, et Ch. Windischmann.
’38. Note sur le développement de la Limace grise. Bull. de l’Acad. de
Brux., Tom. V. pp. 286-296. 1838.
"38. Lztr. from same in Ann. des Sci. nat., 2 sér., Zool., Tom. IX. pp. 366 -
370. 1888.
41. Mémoire sur ’embryogénie des Limaces. 25 pp., 2 pl. Bruxelles.
1841.
VOL. VI. — No. 12. 38
594 BULLETIN OF THE
Also publ. in Beneden, P. J. van, Etudes embryogéniques. pp. 15-39,
Pl. IL, If]. Bruxelles. 1841.
’41*. Recherches sur lembryogénie des Limaces. Arch. f. Anat. Physiol.
. u. wiss. Med., Jahrg. 1841, pp. 176-195, 2 Taf. 1841:
Bischoff, Th. Ludw. Wilh.
’42. Hutwicklungsgeschichte des Kaninchen-Hies. (Gekrénte Preisschrift.)
x + 154 pp., 16 Tab. Braunschweig: .Vieweg u. Sohn. 1842.
'45. Entwicklungsgeschichte des Hunde-Hies. 134 pp., 15 Tab. Braun-
schweig: Vieweg u. Sohn. 1845.
52. Entwicklungsgeschichte des Meerschweinchens. 56 pp., 8 Taf. Gies-
sen: Ricker. 1852.
'77. Historisch-kritische Bemerkungen zu den neuesten Mittheilungen tiber
die erste Entwicklung der Saugethiereier. (Oct. 1876.) 93 pp. Min-
chen: Th. Riedel. 1877.
Blanchard, Raphaél.
'78. La Fécondation dans la série animale d’aprés les publications les plus
récentes. Revue bibliographique. (Dec. 1877.) Jour. de Anat. et de
la Physiol., Tom. XIV. pp. 551-562, 701-762. 31 Aug. and 3 Dec.
1878.
Bobretzky, N.
'76. Studien tiber die embryonale Entwickelung der Gastropoden. Arch.
f. mik. Anat., Bd. XIII. pp. 95-169, Taf. VIIT.-XIII. 15 July, 1876.
"78. Ueber die Bildung des Blastoderms und der Keimblatter bei den In-
secten. (May, 1878.) Zeitschr. f. wiss. Zool., Bd. XXXI. pp. 195 — 215,
Taf. XIV. 6 Sept. 1878.
Brandt, Alexander.
77. Ueber die Eifurehung der Ascaris nigrovenosa. (Herbst, 1876.)
Zeitschr. f. wiss. Zool., Bd. XX VIII. pp. 365 —- 384, Taf. XX., XXI. 8
Mar. 1877.
77°. Bemerkungen iiber die Hifurchung und die Betheiligung des Keimblas-
chens an derselben. (Herbst, 1876.) Zeitschr. f. wiss. Zool., Bd.
XXVIII. pp. 587-606, Taf. XX VII. Figs. 1-28. 23 Apr. 1877.
'78. Ueber das Ei und seine Bildungsstatte. Ein vergleichend-morpho-
logischer Versuch mit Zugrundelegung des Insecteneies. 10 + 200 pp., 4
Taf. Leipzig: Wm. Engelmann. 1878. 3
Brooks, Wm. K. ,
’80. Observations upon the Early Stages in the Development of the Fresh-
water Pulmonates. Studies Biol. Labor. Johns Hopkins University, Ses-
sion 1878-79, No. IL. pp. 73-104, 4 pl. 1880.
Biitschli, O.
73°. Beitrage zur Kenntniss der freilebenden Nematoden. (15 June, 1872.)
Nova Acta Acad. caes. Leop.-Carol., Bd. XXXVI. No. 5, 144 pp., Taf.
XVII.- XXVII. 1873.
'75. Vorlaufige Mittheilung tiber Untersuchungen betreffend die ersten Ent-
wickelungsvorgange im befruchteten Ei von Nematoden u. Schnecken.
Eo ol
MUSEUM OF COMPARATIVE ZOOLOGY. 595
(Dec. 1874.) Zeitschr. f. wiss. Zool., Bd. XXV. pp. 201-213. 1 Mar.
1875.
'75*. Vorlaufige Mittheilung einiger Resultate von Studien iiber die Conjuga-
tion der Infusorien und die Zelltheilung. (May, 1875.) Zeitschr. f. wiss.
Zool., Bd. XXV. pp. 426-441. 25 July, 1875.
75°. Zur Entwicklungsgeschichite des Cucullanus elegans, Zed. (Dec. 1874.)
Zeitschr. f. wiss. Zool., Bd. XXVI. pp. 103-111, Taf. V. 17 Sept.
1875.
'76. Studien iiber die ersten Entwicklungsvorgange der Eizelle, die Zellthei-
lung und die Conjugation der Infusorien. (Nov. 1875.) Abhandlg. d.
Senckenberg. naturf. Gesellsch., Bd. X. pp. 213-464, 15 Taf. 1876.
Also separate, pp. 1-252, 15 Taf. 1876.
76%. Mittheilung uber die Entwicklungsgeschichte der Paludina vivipara.
(12 Aug. 1876.) Zeitschr. f. wiss. Zool., Bd. XX VII. Heft 4, pp. 518-
521. 30 Nov. 1876.
‘77. Zur Kenntniss des Theilungsprocesses der Knorpelzellen. (16 Feb.
1877.) Zeitschr. f. wiss. Zool., Bd. XXIX. pp. 206-215, Taf. XIV.
30 July, 1877.
‘77. Entwicklungsgeschichtliche Beitrage. Zeitschr. f. wiss. Zool., Bd.
XXIX. pp. 216-254, Taf. XV.-XVIII. 30 July, 1877.
Calberla, Ernst.
78. Der Befruchtungsvorgang beim Ei von Petromyzon Planeri. Ein Bei-
trag zur Kenntniss des Baues und der ersten Entw. des befruchteten Wir-
belthiereies. (14 June, 13 August, 1877.) Zeitschr. f. wiss. Zool., Bd.
XXX. Heft. 3, pp. 437-486, Taf. XX VII.—XXIX. 7 Mar. 1878.
Campana.
"77. Note sur la vie et la survie des spermatozoides a I’ intérieur de l’ceuf
chez les Mammiféres. Compt. rend. de l’Acad. des Sci. Paris, Tom.
LXXXIV. No. 2, pp. 91, 92. 8 Jan. 1877.
Carus, Carl Gustav.
'24. Von den aussern Lebensbedingungen der weiss- und kaltbliitigen
Thiere. ine Preisschrift. Nebst zwei Beilagen ttber Entwicklungs-
geschichte der Teichhornschnecke, und iiber Herzschlag und Blut der
Weinbergsschnecke und des Flusskrebses. viii. + 87 pp. 2 Taf. Leipzig:
Gerhard Fleischer. 1824.
’32. Neue Untersuchungen iiber die Entwickelungsgeschichte unserer Fluss-
muschel. Verhandlg. der Leop.-Carol. Akad., Bd. XVI. Abth. 1, pp. 1-
88, Taf. 1-IV. 1832.
Chun, Carl.
'76. Ueber den Bau, die Entwicklung und die physiologische Bedeutung
der Rectaldriisen bei den Insekten. Abhandlg. d. Senckenberg. naturf.
Gesellsch., Bd. X. pp. 27-55, Taf. I-IV. 1876.
Claparéde, Edouard.
59. De la formation et de la Fécondation des ceufs chez les vers Nématodes.
596 BULLETIN OF THE
Mém. de la Soc. de Phys. et d’ Hist. nat. Genéve, Tom. XV. Pt. 1, pp. 1-
102, 8 pl. 1859.
Also separate, 104 pp. 8 pl. Genéve. 1859.
Courvoisier, L. G.
’66. Beobachtungen tiber den sympathischen Grinzstrang, - (Auszug aus
einer von der medicinischen Facultat zu Basel gekronten Preisschrift.)
Arch. f. mik. Anat., Bd. II. pp. 18-45, Taf. Il. 1866.
’68. Ueber die Zcellen der Spinalganglien, sowie des Sympathicus beim
Frosch. Arch. f. mik. Anat., Bd. IV. pp. 125-145, Taf. IX. 1868.
Dallinger, W. H. & J. Drysdale.
77. The Development of the Ovum. Nature, Vol. XVI. Nos. 401, 492,
pp. 178-180, 208-206. 5 and 12 July, 1877.
Also in Month. Mic. Jour., Vol. XVIII. pp. 86-97. 1 Aug. 1877.
Derbés, Alph.
47. Observations sur le mécanisme et les phénoménes qui accompagnent la
formation de embryo chez ’Oursin comestible. Ann. des Sci. nat., 3
sér., Zool., Tom. VIII. pp. 80-98, 1 pl. 1847.
Dieck, Georg.
'74. Beitrage zur Entwickelungsgeschichte der Nemertinen. (26 June,
1873.) Jena. Zeitschr., Bd. VIIL. pp. 500-521, Taf XX., XXI. 1874.
Dujardin, Félix.
’'37. Phénomeénes présentés par des ceufs de limace pondus depuis peu de
temps. Compt. rend. de Acad. des Sci. Paris, Tom. V. pp. 3438, 344.
1837.
Also in L’ Institut, Tom. V. No. 219, Suppl., p. 307. 1837. And Aun. des
Sci. nat., 2 sér., Zool., Tom. VII. pp. 374, 375. 1837.
Dumortier, B. C.
’37. Mémoire sur les evolutions de l’embryon dans les Mollusques gastéro-
podes. (8 May, 1835.) Nouv. Mém. de l’Acad. de Brux., Tom. X.,
47*pp., 4 pl. 1837.
Eberth, C. J.
’63. Ueber den feineren Bau der Lunge. Zeitschr. f. wiss. Zool., Bd. XII.
Heft 4, pp. 427-454, Taf. XIV., XV. 20 Jan. 1863.
"76. Ueber Kern- und Zelltheilung. Arch. f. path. Anat. u. Physiol., Bd.
LXVII. Heft 4, pp. 523-541, Taf. XVITI-XX. 31 Aug. 1876.
Eimer, Theodor.
"71. Die Schnautze des Maulwurfs als Tastwerkzeug. Arch. f. mk. Anat.,
Bd. VII. Heft 3, pp. 181-191, Taf. XVIT. 1871.
"72. Zur Kenntniss vom Baue des Zellkerns. Arch. f. mik. Anat., Bd. VIII.
pp. 141-144. 1 Holzschnitt. 1872.
72°, Untersuchungen iiher die Hier der Reptilien. Arch. f. mik. Anat., Bd.
VIII. pp. 216-248, 397 -434, Taf. XI., XIL, XVII. 1872.
'73. Zoologische Studien auf Capri. 1. Ueber Beroé ovatus. Hin Beitrag
zur Anatomie der Rippenquallen. (June, 1873.) vii +91 pp., 9 pl.
Leipzig: Wm. Engelmann. 1878.
MUSEUM OF COMPARATIVE ZOOLOGY. 597
'77. Weitere Nachrichten tiber den Bau des Zellkerns, nebst Bemerkungen
iiber Wimperepithelien. (8 Feb. 1877.) Arch. f. mik. Anat., Bd. XIV.
Heft 1, pp. 94-118, Taf. VII. 5 May, 1877.
Rev. by HE. Kilein], Quart. Jour. of Mic. Sci., n. ser., Vol. XVIII. No. 70,
po. 107, 198. Apr. 1878:
Ewetsky, Th.
’'75. [Regeneration of Endothelium of the Membrana Descemeti.] Unters.
aus dem path. Inst. zu Zurich, 1875. 3 Heft, p. 98, Taf. V. Fig. 5.
Flemming, Walther.
'74. Ueber die ersten Entwicklungserscheinungen am Ei der Teichmuschel.
(15 Oct. 1873.) Arch. f. mik. Anat., Bd. X. pp. 257-292, Taf. XVI.
Feb. (?) 1874.
'75. Studien in der Entwicklungsgeschichte der Najaden. Sitzungsb. d. k.
Akad. der Wissensch. zu Wien, Mathem.-naturw. Cl., Bd. LX XI. Abth. 3,
pp. 81-212, 4 Taf. 4 Feb. 1875.
'76. Beobachtungen tber die Beschaffenheit des Zellkerns. Arch. f. mik.
Anat., Bd. XIII. pp. 693-717, Taf. XLIT. 20 Oct. 1876.
77. Zur Kenntniss des Zellkerns. (3 May, 1877.) Centralbl. f. d. med.
Wissensch., Jahrg. XV. No. 20, pp. 353-355. 19 May, 1877.
'78. Zur Kenntniss der Zelle und ihrer Theilungserscheinungen. (Aus
einem Vortrag, gehalten im Kieler physiol. Verein den 1. Aug. 1878.)
Schriften des Naturw.Vereins f. Schieswig-Holstein, Bd. III. Heft 1, pp.
23-27. 1878.
78». Beitrage zur Kenntniss der Zelle u. ihrer Lebenserscheinungen. (17
Sept. 1878.) Arch. f. mik. Anat., Bd. XVI. pp. 302-436, Taf. XV.-
ZVI. 20 Dec. 1878.
Feettinger, Alexandre.
_ '76. Recherches sur la structure de l’épiderme des Cyclostomes, et quelques
mots sur les cellules olfactives de ces animaux. Bull. de |’Acad. roy. de
Belg., 2 sér., Tom. XLI. pp. 599-679, 3 pl. 1876.
Fol, Hermann.
’'73. Die erste Entwickelung des Geryonideneies. Jena. Zeitschr., Bd. VII.
pp. 471-492, 3 Holzsch., Taf. XXIV., XXV. Nov. 1878.
"74. Note sur le développement des mollusques Ptéropodes et Céphalopodes.
Arch. de Zool. exp. et gén., Tom. III. No. 3, pp. xxxiii-xlv, Pl. XVIII.
(July no.) Oct. 1874.
75. Sur le développement des Ptérepodes. Compt. rend. de l’Acad. des Sci.
Paris, Tom. LXXX. pp. 196-199. 4 Jan. 1875.
75. Etudes sur le développement des Mollusques. Premier Mémoire sur
le développement des Ptéropodes. Arch. de Zool. exp. et gén., Tom. IV.
pp. 1-214, Pl. I.-X. July— Aug. 1875.
‘75°. Sur le développement des Hétéropodes. Compt. rend. de l’Acad. des
Sci. Paris, Tom. LXXXI. pp. 472-474. 13 Sept. 1875. ;
'75°. Sur le développement des Gastéropodes pulmonés. Compt. rend. de
Acad. des Sci. Paris, Tom. LXXXI. pp. 523-526. 18 Sept. 1875.
598 BULLETIN OF THE
'76. Second Mémoire sur le développement embryonnaire et larvaire des
Hétéropodes. Arch. de Zool. exp. et gén., Tom. V. pp. 105-158, Pl. L-
TV. “Sepa Tere.
'76%. Sur les phénomeénes intimes de la division cellulaire. Compt. rend. de
~ PAcad. des Sci. Paris, Tom. LXXXIIT. No. 14, pp. 667-669. 2 Oct.
1876.
'77. Sur les phénoménes intimes de la fécondation. Compt. rend. de I’ Acad.
des Sci. Paris, Tom. LXXXIV. No. 6, pp. 268-271. 5 Feb. 1877.
'77*. Sur le premier développement d’une Etoile de mer. Compt. rend. de
PAcad. des Sci. Paris, Tom. LXXXIV. No. 8, pp. 357-360. 19 Feb.
ey is
77°. Sur quelques fécondations anormales chez l’Etoile de mer. Compt.
rend. de Acad. des Sci. Paris, Tom. LXXXIV. No. 14, pp. 659-661.
2 Apr. 1877.
"77. Sur le commencement de ’hénogénie chez divers animaux. Bibl. univ.
— Arch. des Sci. phys. et nat. Genéve, nouv. période, Tom. LVIII. No.
232, pp. 439 -472, 26 cuts. (Apr. 15, 1877.)
Reprint with slight additions. Arch. de Zool. exp. et gén., Tom. VI. No. 2,
pp. 145 - 169.
"77°. Sopra i fenomeni intimi della fecondazione degli Echinodermi. Co-
municazione preventiva. Atti. R. Acad. dei Lincei, Transunti, ser. 3,
Vol. I. Fasc. 6, pp. 181-183. 6 May, 1877.
77°, Note sur la fécondation de l’Etoile de mer et de l’Oursin. Compt. rend. —
de Acad. des Sci. Paris, Tom. LXXXV. No. 4, pp. 233-236, 5 fig.
93 July, 1877.
77°, Encore un mot sur la fécondation des Echinodermes. Compt. rend. de
Acad. des Sci. Paris, Tom. LXXXV. No. 14, pp. 625-628. 1 Oct.
LOTT:
‘77. Sur le role du Zoosperme dans la fécondation. Bibl. univ. — Arch.
des Sci. phys. et nat. Genéve, nouv. période, Tom. LX. No. 238, pp. 321
—326. 15 Oct. 1877.
'77, Réponse a quelques objections formulées contre mes idées sur la péné-
tration du zoosperme. Arch. de Zool. exp. et gén., Tom. VI. No. 2, pp.
180-192. 1877. |
"77. Sur la formation des ceufs chez les Ascidies simples. Bibl. univ. —
Arch. des Sci. phys. et nat. Genéve, nouv. période, Tom. LX. No. 238,
pp. 387 —340. 15 Oct. 1877. ,
"79. Recherches sur la fécondation et le commencement de l’hénogénie chez
divers animaux. Mém. de la Soc. de Phys. et d’Hist. nat. Genéve, Tom.
XXVIL. pp. 89-397, Pl. I.-X. 1878-79.
Also separate, 309 pp. Gentve-Bale-Lyon: Henri Georg. 1879.
Frey, Heinr., und Rud. Leuckart. ;
’47. Lehrbuch der Anatomie der wirbellosen Thiere. (Zweiter Theil des
Lehrbuches der Zootomie von Rud. Wagner.) 8+ 626 pp. Leipzig: L.
Voss. 1847.
——_—
MUSEUM OF COMPARATIVE ZOOLOGY. 599
Frommann, C.
65. Ueber die Struktur der Bindesubstanzzellen des Riickenmarks. Vor-
laufige Mittheilung. (21 Jan. 1865.) Centralb. f. d. med. Wissensch.,
Jahrg. III. No. 6, pp. 81-83. 4 Febr. 1865.
’67. Untersuchungen tiber die normale und pathologische Anatomie des
Riickenmarks. Th. Il. pp. 17-48. Jena: Frommann. 1867.
75. Zur Lehre von der Struktur der Zellen. Jena. Zeitschr., Bd. IX. Heft
3, pp. 280-298, Taf. XV., XVI. 31 July, 1875.
Galeb, Osman.
'78*. Organisation et développement des Oxyuridés. Arch. de Zool. exp. et
gén., Tom. VII. pp. 283-390, Pl. XVII.—-XXVI. 1878.
Gegenbaur, Carl.
51. Beitrage zur Entwicklungsgeschichte der Landgastropoden. Zeitschr.
f. wiss. Zool., Bd. III. Heft 4, pp. 371-411, Taf. X.-XII. 15 Feb. 1851.
52. Entwickelung von Limax. Verhandlg. d. phys. med. Gesellsch. in
Wurzburg. Bd. IIL. pp. 162, 163. 1852.
"52°. Lebende Doppelmissbildung von Limax. Ibid., pp. 166, 167.
’57. Ueber die Entwickelung der Sagitta. Abhandlg. d. Senckenberg. naturf.
Gesellsch. zu Halle, Bd. IV. Heft 1, pp. 1-18, Taf. I. 1856.
Also separate, Halle: Schmidt. 1857.
'74. Grundriss der vergleichenden Anatomie. viii + 660 pp., 320 Holz-
schnitten. Leipzig: Wm. Engelinann. 1874.
Giard, Alfred.
76. L’ceuf et les débuts de lévolution. Bull. sci. Dépt. du Nord, No. 12,
p: 252. Lille. 1876.
'76’. Abstr. by R. Hertwig iz Hofmann u. Schwalbe’s Jahresberichte, Bd.
V. 2% Abtheilung, p. 485. 1878.
'76%. Note sur Vembryogénie de la Salamacina Dysteri, Hux. Compt.
rend. de l’Acad. des Sci. Paris, Tom. LXXXII. No. 3, pp. 283-235. 17
Jan. 1876.
77. Sur les modifications que subit Pceuf des Méduses phanérocarpes avant
la fécondation. Compt. rend. de I’ Acad. des Sci. Paris, Tom. LXXXIV.
No. 12, pp. 564-566. 19 Mar. 1877.
'77. Note sur les premiers phénoménes du développement de lOursin
(Kchinus miliaris). (See also transl. Giard, '774.) Compt. rend. de
Acad. des Sci. Paris, Tom. LXXXIV. No. 15, pp. 720-722. 9 Apr.
USTT.
"77, Sur la fécondation des Echinodermes. Compt. rend. de l’Acad. des
Sci. Paris, Tom. LXXXV. No. 7, pp. 408-410. 13 Aug. 1877.
77°. On the First Development of Echinus miliaris. (Zraus. of 77°.) Ann.
and Mag. of Nat. Hist., ser. 4, Vol. XIX. No. 113, pp. 4384-436.
May, 1877.
Gibbes, Heneage.
’80. On the Structure of the Spermatozoén. Quart. Jour. of Mic. Sci., n.
ser., Vol. XX. No. 79, pp. 320-321. 1 July, 1880.
600 BULLETIN OF THE
Goette, Alexander.
‘75. Die LKntwickelungsgeschichte der Unke (Bombinator igneus) als
Grundlage einer vergleichenden Morphologie der Wirbelthiere. Mit einem
Atlas von 22 Taf. Leipzig: Leopold Voss. 1875.
Greeff, Richard.
'71. 1. Ueber die Actinophryen oder Sonnenthierchen des siissen Was-
sers als echte Radiolarien, zur Familie der Acanthometriden gehdrig.
Il. Ueber die Fortpflanzung der Actinophryen. Sitzsungsb. d. Nieder-
rhein. Gesellsch. f. Naturf- u. Heilkunde, Bonn, pp. 4-9. 9 Jan. 1871.
'76. Ueber den Bauder Echinodermen. Vierte Mittheilung. Sitzungsb. der
Gesellsch. zur Beférderung der gesammten Naturw. zu Marburg, Jahrg.
1876, No. 1, pp. 16-37. 13 Jan. 1876. | )
76%. Ueber den Bau und die Entwickelung der Echinodermen. Finfte Mit-
theilung. Ibid., Jahrg. 1876, No. 5, pp. 883-95. 18 May, 1876.
Grenacher, H.
69. Bemerkungen tiber Acanthocystis viridis, Ehbg. sp. (Acanthocystis
Carter, gen. in Ann. & Mag. of Nat. Hist., 3 ser., Vol. XII, XIII.) (10
Dec. 1868.) Zeitschr. f. wiss. Zool., Bd. XIX. Heft 2, pp. 289 — 296,
Taf. XXIV. Fig. 1-3. 1 July. 1869.
Grobben, Carl.
‘78. Beitrage zur Kenntniss der mannlichen Geschlectsorgane der Deka-
poden nebst vergleichenden Bemerkungen itiber die der tibrigen Thora.
costraken. (1 Feb. 1878.) Arbeiten a. d. Zool. Institut zu Wien, Bd. I.
Heft 1, pp. 57-150, Taf. VI.—XI. 1878.
"79. Die Entwickelungsgeschichte der Moina rectirostris. Zugleich ein Bei-
trag zur Kenntniss der Anatomie der Phyllopoden. Arbeiten a. d. Zool.
Institut zu Wien, Bd. II. Heft 2, pp. 2038-268, Taf..XI.-XVII. 1879.
Abstr. in English by J. 8. Kingsley iz Amer. Naturalist, Vol. XIV. No. 2,
pp. 114-116, 1 pl. Feb. 1880.
Grube, Adolph Eduard.
’44. Untersuchungen tiber die Entwicklung der Clepsmen. vi + 56 pp,
Tab. 1-UI. Ké6nigsberg: Gebr. Borntrager. 1844.
Haeckel, Ernst.
'74. Anthropogenie oder Entwickelungsgeschichte des Menschen. xviii +
732 pp., 12 Taf., 210 Holzsch., 36 genet. Tab. Leipzig: Wm. Engel-
mann. 1874.
"74°. Die Gastreea-Theorie, die phylogenetische Classification des Thierreichs
und die Homologie der Keimblatter. (29 Sept. 1873.) Jena. Zeitschr.,
Ba) Vil pp. 1-55, Taft eye
"75. Die Gastrula und die Hifurchung der Thiere. (4 Oct. 1875.) Jena.
Zeitschr., Bd. IX. pp. 402 - 508, Taf. XIX.-XXV. 1875.
Harless, E. ; mn,
46. Briefliche Mittheilung tiber die Ganglienkugeln der Lobi electrici von
Torpedo Galvanii. Arch. f. Anat. Physiol. u. wiss. Med. Jahrg. 1846,
pp. 283-291, Taf. X. Figs. 1-9. 1846.
EY
MUSEUM OF COMPARATIVE ZOOLOGY. 601
Hatschek, B.
"77%. Embryonalentwicklung und Knospung der Pedicellina echinata.
(June, 1877.) Zeitschr. f. wiss. Zool., Bd. XXIX. Heft 4, pp. 502-
549. Taf. XX VIII-XXX., 4 Holzschn. 18 Oct. 1877.
78. Studien tiber Entwicklungsgeschichte der Anneliden. Arbeiten a. d.
zool. Institut zu Wien, Bd. I. Heft. 3, pp. 277-404, Taf. XXIIT.-XXX.
1878.
Heitzmann, C.
'73. Untersuchungen tiber das Protoplasma. I. Bau des Protoplasmas.
II. Das Verhaltniss zwischen Protoplasma u. Grundsubstanz im Thier-
kérper. Sitzungsb. d. k. Akad. der Wisseusch. Wien, Mathem.-naturw.
Cl., Bd. LX VII. Abth. 3, pp. 100-115, 141-160, 2 pl. 17 Apr., 23 Mai,
1873.
"73°. Same. ILI. Die Lebensphasen des Protoplasma. IV. Die Entwicke-
lung der Beinhaut, des Knochens u. des Knorpels. V. Die Entziiudung
der Beinhaut, des Knochens u. des Knorpels. Sitzungsb. d. k. Akad.
der Wissensch. Wien, Mathem.-naturw. Cl., Bd. LXVIII. Abth. 3,
pp. 41-50, 56-67, 87-104, 3 Taf. 26 June, 10 July, 24 July, 1874.
Helm, F. E.
"76. Ueber dis Spinndriisen der Lepidopteren. Zeitschr. f. wiss. Zool., Bd.
XXVI. Heft 4, pp. 434-469, Taf. XX VII, XXVIII. 6 Mar. 1876.
Henneguy, L. Felix.
’80. Note sur lexistence de globules polaires dans l’ceuf des Crustacés.
Bull. Soc. Philomatique, Paris, sér. 7, Tom. IV. No. 3, p. 135. 10 Apr.
1880.
Transl. under title, On the Existence of Polar Globules in the Ovum of Crus-
tacea. Ann. & Mag. Nat. Hist., 5 ser., Vol. VI. No. 36, p. 465. Dec.
1880.
Hensen, Victor.
'75. Beobachtungen iiber die Befruchtung und Entwicklung des Kaninchens
und Meerschweinchens. Zeitschr. f: Anat. u. Entw., Bd. I. pp. 213-
273, Taf. VIIL—XII. 26 Nov. 1875.
Hertwig, Oscar.
75. Beitrage zur Kenntniss der Bildung, Befruchtung und Theilung des
thierischen Kies. Morph. Jahrbuch, Bd. I. Heft 3, pp. 347-434, Taf. X.-
ME 1875. ;
Also as Wabilitations Schrift. Leipzig. Aug. 1875.
77. Same. Zweiter Theil. (Sept. 1876.) Morph. Jahrbuch, Bd. III. pp.
1-86, Taf. I1-V. 1877.
77°. Weitere Beitrage zur Bildung, ete. (Febr. 1877.) Morph. Jahrbuch,
Bd. III. pp. 271-279. May, 1877.
'77°. Nouvelles contributions a la connaissance de la formation de la fécon-
dation et du fractionnement de l’ceuf des animaux. (Zransl. by Hermann
Fol of O. Hertwig, ’77°, “ Weitere Beitrage,” etc.) Arch. de Zool.
exp. et gén:, Tom. VI. No. 2, pp. 171-179. 1877.
602 BULLETIN OF THE
'78. Beitrage zur Kenntniss der Bildung, Befruchtung und Theilung des
thierischen Kies. Dritter Theil, Erste Abtheilung. (19 May, 1877.)
Morph. Jahrbuch, Bd. [V. Heft 1, pp. 156-175, Taf. VI-VIII. 1878.
78°. Beitrage zur Kenntniss der Bildung, ete. Dritter Theil, II. Abschnitt.
(12 June, 1877.) Morph. Jahrbuch, Bd. IV. Heft 2, pp. 177-218, Taf.
IX.-Xl. 1878.
Hertwig, Richard.
76%. Beitrage zur einer einheitlichen Auffasung der verschiedenen Kern-
formen. (2 Dec. 1875.) Morph. Jahrbuch, Bd. II. Heft 1, pp. 63-82,
Pat Dit? 21676;
His, Wilhelm.
'75. Untersuchungen tiber die Entwickelung von Knochenfischen, beson-
ders uber diejenige des Salmens. Zeitschr. f. Anat. u. Entw., Bd. I.
Hefte 1 u. 2, pp. 1-40, Taf. I., IL., 14 Figs. 1 May, 1875.
Flock, 2.3P::C:
'76. Zur Entwickelungsgeschichte der Entomostraken. I. Embryologie von
Balanus. Niederlandisches Arch. f. Zool., Bd. III. Heft 1, pp. 47 - 82,
Raf. TEES TV. - ai May, 1876,
Hoffmann, C. K.
‘77. Zur Anatomie und Ontogenie von Malacobdella. Niederlandisches
Arch. f. Zool., Bd. IV. Heft 1, pp. 1-29, Taf. I., II. Nov. 1877.
‘77°. Zur Entwickelungsgeschichte der Clepsinen. Hin Beitrag zur Kennt-
niss der Hirudineen. (5 Aug. 1877.) Niederlandisches Arch. f. Zool.,
Bd. IV;. Heft 1, pp. 31-54; Taf,,.TIE.,. 1V.- Nov. 1877.
’80. Vorlaufige Mittheilung zur Ontogenie der Knochenfische. (29 Nov.
1880.) Zool. Anzeiger, Jahrg. III. Nos. 71, 72, pp. 607 - 610, 629 - 634.
13 and 27 Dec. 1880.
Jhering, Hermann von.
'75. Ueber die Entwicklungsgeschichte von Helix. Zugleich ein Beitrag zur
vergleichenden Anatomie und Phylogenie der Pulmonaten. Jena. Zeitschr.,
Bd. IX. Heft 3, pp. 299 - 338, Taf. XVII, XVIII. 31 July, 1875.
'77. Zur Kenntniss der Wibildung bei den Muscheln. (2 Jan. 1877.)
Zeitschr. f. wiss. Zool., Bd. XXIX. Heft 1, pp. 1-14, Taf. I. 26 June,
1877.
'78. Befruchtung und Furchung des thierischen Hies und Zelltheilung nach
dem gegenwartigen Stand der Wissenschaft dargestellt. Mit 10 Ab-
bildg. (10 Dec. 1877.) Vortrage fiir Thierarzte, redig. v. Prof. Dr. J.
a te G. Pflug, ser. 1, Heft 4, pp. 101-156. Leipzig: Herm. Dege. 1878.
ebs.
'74. Die Regeneration des Plattenepithels. (Mitgetheilt im Verein deut-
scher Aerzte in Prag, 13. Marz 1874.) Archiv. f. exp. Path. u. Pharma-
kol., Bd. IIT. p. 125, Taf. IT.
Klein, E.
'78. Observations on the Structure of Cells and Nuclei. Quart. Jour. of
Mic. Sci., n. ser., Vol. XVIII. No. 71, pp. 315-339, Pl. XVI. July,
1878.
MUSEUM OF COMPARATIVE ZOOLOGY. 603
"79. Same. Il. Quart. Jour. of Mic. Sci., n. ser., Vol. XIX. No. 74,
pp leery, Pl. Vil Apr. 1879:
Kleinenberg, Nicolaus.
"72. Hydra Hine anatomisch-entwicklungsgeschichtliche Untersuchung.
vi + 90 pp., 4 Taf. Leipzig: Wm. Engelmann. 1872.
Kolliker, Albert von.
43. Beitrage zur Entwickelungsgeschichte wirbelloser Thiere. I. Ueber
die ersten Vorgange im befruchteten Ei. Arch. f. Anat. Physiol. u. wiss.
Med., Jahrg. 1843, pp. 68-141, 2 Taf. 1843.
57. Untersuchungen zur vergleichenden Gewebelehre, angestellt in Nizza
im Herbste 1856. Verhandlg. d. phys. med. Gesellsch. in Wurzburg,
Bd. VIII. Heft 1, pp. 1-128, Taf. 1-11. 1857.
’63. Handbuch der Gewebelehre des Menschen. Fir Aerzte und Studie-
rende. 4% Aufl. 22 + 730 pp., 898 Holzschn. Leipzig: Wm. Engel-
mann. 1863.
Korotneff, A.
76. Histologie de l’Hydre et de la Lucernaire. Arch. de Zool. exp. et
gén., Tom. V. pp. 369-400, Pl. XV., XVI. 1876.
Kowalevsky, A.
66°. Entwickelungsgeschichte der einfachen Ascidien. (1 Nov. 1866.)
Mém. de l’Acad. imp. des Sci. de St. Pétersbourg, sér. 7,"Tom. X. No. 15,
19 pp., 3 Taf. 1866.
"71. Embryologische Studien an Wiirmern und Arthropoden. (Présenté
18 Nov. 1869.) Mém. de l’Acad. imp. des Sci. de St. Pétersbourg, sér. 7,
Tom. XVI. No. 12, 70 pp., 12 Taf. 1871.
"75. Ueber die Entwickelungsgeschichte der Pyrosoma. Arch. f. mik.
Anat., Bd. XI. pp. 597-635, Taf. XXXVII-XLI. 1875.
Krohn, August.
’49. Beitrag zur Enwicklungsgeschichte der Seeigelarven. 36 pp., 2 Taf.
Heidelberg: Groos. 1849.
"52. Ueber die Entwickelung der Ascidien. Arch. f. Anat. Physiol. u. wiss.
Med., Jahrg. 1852, pp. 312-333. 1852.
53. Transl. of same w. Figs. Scientific Memoirs, etc., Nat. Hist., pp. 312 -
329. London: Taylor and Francis. 1853.
Kupffer, Carl.
70. Die Stammverwandtschaft zwischen Ascidien und Wirbelthieren. Nach
Untersuchungen tiber die Entwicklung der Ascidia canina (Zool. dan.).
Arch. f. mik. Anat., Bd. VI. pp. 115-172, Taf. VITL-X. 1870.
'72. Zur Entwickelung der einfachen Ascidien. I. Die Gattung Molgula.
II. Das Nervensysten der Larve von Asc. mentula, Zool. dan. Arch. f.
mik. Anat., Bd. VIII. pp. 358 - 396, Taf. XVII. 1872.
'74. Die Speicheldriisen von Periplaneta (Blatta) orientalis u. ihr Nerven-
apparat. Beitrage zur Anat. u. Physiol., als Festgabe Carl Ludwig zum
15. October 1874 gewidmet von seinen Schiilern, pp. Ixiv-Ixxxi. Taf.
IX. Leipzig. 1874.
604 BULLETIN OF THE
'75. Ueber Differenzirung des Protoplasma an den Zellen thierischer Gewebe.
(Nach einem in physiol. Verein zu Kiel gehaltenen Vortrage.) Schriften
des naturw. Vereins f. Schleswig- Holstein, Bd. L. Heft 8, pp. 229-242.
1875.
Kupffer, Carl, und B. Benecke.
'78. Der Vorgang der Befruchtung am Ei der Neunniete Herrn Theodor
Schwann zur Feier seiner vierzigjahrigen Lehrthatigkeit am 23. Juni 1878
als Festschrift gewidmet v. d. med. Facultat d. Albertus Univ. zu Kénigs-
berg in Preussen. 24 pp.,1 pl. Kdonigsberg: Hartung. 1878.
Lang, Arnold.
'78. Die Dotterfurchung von Balanus. Jena. Zeitschr., Bd. XII. pp. 671-
674, Lat XX.» SOT 1878. :
Langerhans, Paul. 3
“71. Ein Beitrag zur Anatomie der sympathischen Ganglienzellen. (Habili-
tationsschrift.) Freiburg. 1871.
73°. Ueber die Haut der Larve von Salamandra maculosa. Arch. f. mik.
Anat., Bd. IX. pp. 745-852, Taf. XXXI. 1878.
Langhans, Theodor.
'76. Zur Lehre von der Zusammensetzung des Kerns. Centralbl. f. d.
med. Wissensch., Jahrg. XIV. No. 50, pp. 882-884. 9 Dec. 1876.
Lankester, E. Ray. |
73. Summary of Zodlogical Observations made at Naples in the Winter of
1871-72. Ann. and Mag. of Nat. Hist., 4 ser., Vol. XI. No. 62, pp. 81-
97.2) Beh iBYS:
'74. Observations on the Development of the Pond-snail (Lymneus stagna-
lis), and on the Early Stages of other Mollusca. Quart. Jour. of Mic.
Sci, n. ser., Vol. XIV: No. 56,-pp:.365-391, Pl. XVI, XVI. Wee
1874.
"75. Observations on the Development of the Cephalopoda. Quart. Jour. of
Mic. .Sci., n. ser., Vol. XV. No. 57, pp. 37-47, PI. 1V., V. dam. 67a:
"75%. Contributions to the Developmental History of the Mollusca. (Rec’d
19 Jan., read 12 Mar. 1874.) Phil. Trans. Roy. Soc. Lond., Vol.
CLAV Pt. 15/48 :pp4 Llp S75:
Laurent, J. L. Maur.
35°. Observations sur le iMrelapnonient: des ceufs de la Limace grise
[= flavus] et de la Limace rouge. Ann. des Sci. nat., sér. 2, Zool., Tom.
IV. pp. 248-250. 1835. )
37. Suite des observations sur le développement des Limaces et autres
Mollusques gastéropodes. Compt. rend. de Acad. des Sci. Paris, Tom.
IV. pp. 295-297. 20 Feb. 1837.
’37°.. Faits pour servir a l’histoire générale du développement des ani-
maux. (1. Ces faits sont présentés pour donner une idée gén. de la
composition de l’ceuf et du mechanisme de l’organogénie dans la série
animal.) Ann. frang. et étrang. d’Anat. et de Physiol., Tom. I. pp. 16-27.
1837.
MUSEUM OF COMPARATIVE ZOOLOGY. 605
37°. Same. 2°Article: Essai sur la détermination des organes génitaux
des hélices, de la vésicule ombilicale et de la rame caudale des embryons
de /imaces et des hélices. Ann. frang. et étrang. d’Anat. et de Physiol.,
Tom. 1. pp. 252-268, Pl, VIL, VIII. 1837.
’38. Same. 3°Article: Exposé des resultats obtenus dans des recherches
sur les ceufs, et le develop. des limaces et autres mollusques, et considera-
tions générales sur la zoogénie. Ann. frang. et étrang. d’Anat. et de Phy-
siol., Tom. II. pp. 1383-157, 333-335, Pl. III. 1838.
’38". Recherches sur la zoogénie, premiers résultats des observation sur le
développement des organs glandulaires des Zimaces. Ann. franc. et
étrang. d’ Anat. et de Physiol., Tom. II. pp. 325-335. 1838.
Laurent, Paul.
’42. Sur le développement du Limax agrestis. HExtr. des Procés-verb. des
Séances de la Soc. philomatique, 1842, pp. 45, 46. 1842.
Lavdowsky, M.
76. Untersuchungen tiber den akustichen Endapparat der Saugethiere.
Arch. f. mik. Anat., Bd. XIII. pp. 497-557, Taf. XXXII.-XXXV. 20
Oct. 1876. |
Leuckart, Rudolph.
53. Zeugung. Wagner’s Handworterbuch der Physiologie mit Ricksicht
auf physiologische Pathologie, Bd. IV. pp. 707-1000. 1853.
’67-76. Die menschlichen Parasiten und die von ihnen herrihrenden Krank-
heiten. Ein Hand- und Lehrbuch fiir Naturforscher und Aerzte, Bd. II.
8 + 882 pp., 401 Holzschn. Leipzig u. Heidelberg: C. F. Winter.
1867-76.
Leydig, Franz.
’49. Zur Anatomie von Piscicola geometrica mit theilweiser Vergleichung
anderer einheimischer Hirudineen. Zeitschr. f. wiss. Zool., Bd. I. Heft 2,
pp. 103-134, Taf. VIII.-X. 1849.
’54. Ueber den Bau und die systematische Stellung der Raderthiere. Zeit-
schr. f. wiss. Zool., Bd. VI. Heft 1, pp. 1-20, Taf. I-IV. 22 July,
1854.
’57. Lehrbuch der Histologie des Menschen und der Thiere. xii + 551
pp., 271 Holzschn. Frankfurt a. M.: Meidinger, Sohn & Comp. 1857.
60. Naturgeschichte der Daphniden (Crustacea Cladocera). iv + 252 pp.,
10 Taf. Tubingen: Laupp’sche Buchh. 1860.
Lieberkiihn, N.
49. De gangliorum structura penitiori. (Dissertation.) Berl. 1849.
Lovén, Ss. L.
’48. Ueber die Entwickelung der kopflosen Mollusken. Arch. f. Anat.
Physiol. u. wiss. Med., Jahrg. 1848, pp. 5381-561. 1848.
’48*, Bidrag till kannedomen om utvecklingen af Mollusca Acephala Lamel-
libranchiata. K. Vetensk. Akad. Handler., pp. 324-436, 6 pl. 1848.
Also separate, 109 pp., 6 pl. Stockholm: Norstedt & Soner. 1850.
606 BULLETIN OF THE
Ludwig, Hubert.
"75. Ueber die Ordnung Gastrotrichia Metschn. (11 June, 1875.) Zeit-
schr. f. wiss. Zool., Bd. XXVI. Heft 2, pp. 193-226, Taf. XIV. 8 Dec.
1875.
'76. Ueber die Bildung des Blastoderms bei den Spinnen. (24 Jan. 1876.)
Zeitschr. f. wiss. Zool., Bd. XXVI. Heft. 4, pp. 470-485, Taf. XXIX.,
XXX. 6 Mar. 1876.
McCrady, John.
77. A Provisional Theory of Generation. Proc. Bost. Soc. Nat. Hist., Vol.
XIX. pp. 171-185. 18 Apr. 1877.
Mark, Edward L.
'79*. On carly stages in the embryology of Limax campestris. (10 July, '
1879.) Zool. Anzeiger, Jahrg. II. No. 38, pp. 493-496. 22 Sept. 1879.
Mayer, Paul.
27. Zur Entwicklungsgeschichte der Dekapoden. (12 Apr. 1877.) Jena.
Zeitschr., Bd. XI. Heft 2, pp. 188-269, Taf. XIII.-XV. 15 June,
IS#F-
"78. Carcinologische Mittheilungen. Mittheil. aus d. Zool. Station zu Nea-
pel., Bd. I. Heft 1, pp. 40-53, Taf. I., 4 Holzschn. 1878.
Mayer, Sigmund.
"72. Das sympathische Nervensystem. Stricker’s Handbuch der Lehre von
den Geweben, Capitel XXXII. pp. 809-821. 1872.
Mayzel, Waclaw O.
"75. Ueber ecigenthiimliche Vorgange bei der Theilung der Kerne in Epi-
thelialzellen. Vorlaufige Mittheiluug. Centralbl. f. d. med. Wissensch.,
Jahrg. XTIT. No. 50, pp. 849-852. 20 Nov. 1875.
"753, Same. (Polish.) Medycyn, No. 45. Warsaw. 1875.
"76. Beitrage zur Lehre von dem Theilungevorgang des Zellkerns. Gazeta
lekarska, No. 27. 1876. (Poltsh.)
"76°, Abstr. in Protok. d. Situnzgen d. Section fir Zool. u. vergl. Anat.
der 5. Versammlung russischer Naturforscher u. Aerzte in Warschau im
Sept. 1876. (Russian.)
"76>. Renort on Same by Hoyer in Centralbl. f. d. med. Wissensch., Jahrg.
XV. No. 11, pp. 196-199. 17 Mar. 1877.
"76°. Abstr. by Hoyer in Zeitschr. f. wiss. Zool., Bd. XXVIII. pp. 399,
400. 8 Mar.-1877.
"76%. Abstr. by Hoyer und Mayzel iz Hofmann u. Schwalbe’s Jahresberichte,
Bd. V. Anat. Abth., pp. 36, 37. 1878.
'77. Weitere Beitrage zur Lehre von Theilungsvorginge der Zellkerne.
(Polish.) Gazeta lekarska, Vol. XXIII. No. 26. 27 June, 1877.
77°, Report by Hoyer in Centralbl. f. d. med. Wissensch., Jahrg. XV.
No. 44, pp. 791-793. 3 Nov. 1877.
77> Rey. in Hofmann u. Schwalbe’s Jahresberichte, Bd. VI., Anat. Abth.,
pp. 25, 26.
MUSEUM OF COMPARATIVE ZOOLOGY. 607
'78. Ueber die Regeneration der Epithelien und die Zelltheilung. I. Theil,
127 pp. (Russian.) (Arbeiten aus den Laboratorien der medic. Facul-
tat der Universitat in Warschau, unter Redaction von F. Nawrocki,
Heft 4. Mar. 1878.)
Abstr. by Mayzel in Hofmann u. Schwalbe’s Jahresberichte, Bd. VIT., Anat.
Abth., p. 45.
'78*. Ueber die ersten Veranderungen des befruchteten thierischen Hies und
iiber die Zelltheilung. (Podish.) Denkschr. der Warschauer arztlichen
Gesellsch. Heft III. p. 593. 1878.
Rev. by Mayzel ix Hofmann u. Schwalbe’s Jahresberichte, Bd. VII., Anat.
Abth., p. 27. ;
'79. Ueber die Vorgange bei der Segmentation des Kies von Wirmern
(Nematoden) und Schnecken. Zool. Anzeiger, Jalrg. Il. No. 29,
pp. 280-282. 26 May, 1879.
'79*. Ueber die Vorgange bei der Segmentation des Eies von Wirmern
(Nematoden) und Schnecken. (Polish. Communicated in the biological
session of the Warsaw Med. Soc., 26 Nov. 1878.) Gazeta lekarska
(Med. Gazetie), No. 4. Jan. 1879.
"79°. Also in Memoirs of the Warsaw Med. Society, 1879, Heft 1.
'79°. Abstr. by Mayzel ix Hofmann u. Schwalbe’s Jahresberichte, Bd. VIL.,
Anat. Abth., pp. 26, 27.
Meckel von Hemsbach, Heinrich.
’46. Mikographie einiger Driisenapparate der niederen Thiere. Arch. f.
Anat. Physiol. u. wiss. Med., Jahrg. 1846, pp. 1-73, Taf. I-III. 1846.
52. Die Bildung der fur partielle Furchung bestimmten Kier der Vogel,
im Vergleich mit dem Graafschen Follikel der Decidua des Menschen.
Zeitschr. f. wiss. Zool., Bd. IIL. Heft 4, pp. 420-434, Taf. XV. 1852.
Meissner, Georg.
’'54. Beobachtungen tber das Hindringen der Samenelemente in den Dotter.
No. IL. u. Il. Zeitschr. f. wiss. Zool., Bd. VI. Heft 2, pp. 208-264,
272-295, Taf. VI., VIL, IX. 14 Sept. 1854.
’54*. Beitrage zur Anatomie und Physiologie von Mermis albicans. (6 Aug.
1853.) Zeitschr. f. wiss. Zool., Bd. III. Hefte 2 u. 3, pp. 207-284,
Taf. XI-XV. 19 Dec. 1853.
’56. Ueber die Befruchtung des Hies von Echinus esculentus. Verhandlg.
d. naturf. Gesellsch. in Basel, Bd. I. Heft 3, pp. 374, 875. 1856.
Metschnikoff, Elias.
’66. Embryologische Studien an Insecten. Zeitschr. f. wiss. Zool., Bd.
XVI. Heft 4, pp. 389-500, Taf. XXIII.-—XXXII. 6 Dec. 1866.
69. Studien tiber die Entwickelung der Echinodermen und Nemertinen.
(18 Mar. 1869.) Mém. de l’Acad. imp. des Sci. de St. Pétersbourg,
7 sér., Tom. XIV. No. 8, 73 pp., 12 Taf.
69%. Separate, with above title. 2+ 73 pp, 12 Taf. 1869.
'74. Studien tiber die Entwickelung der Medusen und Siphonophoren.
608 BULLETIN OF THE
(5 July, 1872.) Zeitschr. f. wiss. Zool., Bd. XXIV. pp. 15-83, Taf. II.-
XIL., 8 Holazschn. 12 Feb. 1874.
Minot, Charles Sedgwick.
"77°, Account of the Recent Investigations of Embryologists on the Forma-
tion of the Germinal Layers and of the Phenomena of Impregnation among
Animals. Proc. Bost. Soc. Nat. Hist., Vol. X1X., pp. 165-171. 18
Apr. 1877.
Miiller, A.
’64. Ueber die Befruchtungserscheinungen im Hi der Neuenaugen. Schrif-
ten d. k. phys-dkonom. Gesellsch. zu Konigsberg, Jahrg. V. pp. 109-
419. 1864.
Miiller, Friedrich.
48. Zur Kenntniss des Furchungsprocesses im Sehneckeneie. Arch. f. Na-
ture., dabre, XTV. Bd. T. pp. 1-6, Tat) EP aaisas,
Miiller, Johannes.
’52. Ueber die Erzeugung von Schnecken in Holothurien. Arch. f. Anat.
Physiol. u. wiss. Med., Jahrg. 1852, pp. 1-36.
52%. Ueber Synapta digitata und tber die Erzeugung von Schnecken in
Holothurien. iv + 36 pp., 10 Taf. Berlin: G. Reimer. 1852.
Munk, Hermann.
58. Ueber Ei- und Samenbildung und Befruchtung bei den Newauides
(Apr. 1858.) Zeitschr. f. wiss. Zool., Bd. IX. Heft 3, pp. 365-416,
Taf. XIV., XV. 11 Oct, 1858.
Oellacher, Josef.
"70. Untersuchungen itiber die Furchung und Blatterbildung im Hihnereie.
Studien aus dem Institute fiir experimentelle Pathologie, herausg. von 8.
Stricker. I. Wien. 1870.
72. Beitrage zur Geschichte des Keimblaschens im Wirbelthiereie. Arch.
f. mik. Anat., Bd. VIII. pp. 1-27, Taf. 1. 1872.
"72. Beitrage zur Entwicklungsgeschichte der Knochenfische nach Beobach-
tungen am Bachforelleneie. Zeitschr. f. wiss. Zool., Bd. XXII. Heft 4,
pp. 373-421, Taf. XXXIT., XXXITI. 20 Sept. 1872.
"74, Ueber eine im befruchteten Forellenkeim vor den einzelnen Furchungs-
acten zu beobachtende radiare Structur des Protoplasma. Berichte d.
naturw.-med. Verein zu Innsbruck, Bd. IV. 1874: (?).
Peremeschko.
78. Ueber die Theilung der Zellen. Vorlaufige Mittheilung. Centralbl. f.
d. med. Wissensch., Jahrg. XVI. No. 30, pp. 547, 548. 27 July, 1878.
"78°, Ueber die Theilung der thierischen Zellen. (Preliminary communication
in Russian.) Medicin. Bote. 1878, No. 31. 5 Aug. 1878.
"78°, Rev. by Ebner iz Hofmann u. Schwalbe’s Jahresberichte, Bd. VIL,
Anat. Abth., p. 15:
Pérez, J.
77, Sur la fécondation de l’ceuf chez l’Oursin. Compt. rend. de P Acad. des
Sci. Paris, Tom. LXXXIV. No. 13, pp. 620-622. 26 Mar. 1877.
{es gros x — eg ——— “ 5 -
x PS ete os a eee Seas
ae ss ee.
MUSEUM OF COMPARATIVE ZOOLOGY. 609
'77°. Observations relatives aux opinions émisse par M. H. Fol, le 23 juillet
dernier, sur la fécondation de l’ceuf chez l’Astérie et chez l’Oursin.
Compt. rend. de l’Acad. des Sci. Paris, Tom. LXXXV. No. 6, pp. 353,
354. 6 Aug. 1877.
'79. Recherches sur les phénoménes qui précedent la segmentation de Pceuf
chez |’Hélice (H. aspera). Jour. de Anat. et de la Physiol., Vol. XV.
pp. 329-401, Pl. XXVII., XXVIII... Aug. 1879.
Pfliger, E. F.,.W.
’63. Ueber die Hierstocke der Saiugethiere und des Menschen. 124 pp., 5
Taf. Leipzig: Engelmann. 28 Mar. 1863.
Priestley, John.
"76. Recent Researches on the Nuclei of Animal and Vegetable Cells, and
especially of Ova. Quart. Jour. of Mic. Sci., n. ser., Vol. XVI. pp. 131-
152, Pl. XI., XII. Apr. 1876.
Purkinje, Joan. Evang.
30. Symbole ad ovi avium historiam ante incubationem. Adjecte sunt
tab. due lith. Lipsie: L. Voss. 1830.
Quatrefages, Armand de.
’48. Etudes embryogéniques. Mémoire sur l’embryogénie des Annélides.
Ann. des Sci. nat., 3 sér., Zool., Tom. X. pp. 153-201. 1848.
Rabl, Carl.
'75. Die Ontogenie der Siisswasser-Pulmonaten. Jena. Zeitschr., Bd. IX.
pp. 195-240, Taf. VII.-IX. 1875.
'76. Ueber dic Entwicklungsgeschichte der Malermuschel. Jena. Zeitschr.,
Bd. X. pp. 310-393, Taf. X.- XII. 31 Aug. 1876.
Ratzel, Fritz.
69. LBeitrage zur anatomischen und systematischen Kenntniss der Oligo-
chaeten. Zeitschr. f. wiss. Zool., Bd. XVIII. Heft 4, pp. 563-591, Taf.
XLII. 1 Feb. 1869.
69". Vorlaufige Nachricht iber die Entwickelungsgeschichte von Lumbricus
u. Nephelis. (13 Aug. 1868.) Zeitschr. f. wiss. Zool., Bd. XIX. Heft 2,
pp. 281-283. 1 July, 1869.
Ratzel, Fritz, und M. Warschawsky.
‘69. Zur Entwickelungsgeschichte des Regenwurms (Lumbricus agricola
Hoffm.). Zeitschr. f. wiss. Zool., Bd. XVIII. pp. 546-562, Taf. XLI.
1 Feb. 1869.
Reichert, Karl Bogislaus.
46. Der Furchungsprocess und die sogenannte Zellenbildung um Inhaltspor-
tionen. Arch. f. Anat. Physiol. u. wiss. Med., Jahrg. 1846, pp. 196-282,
Taf. IX. 1846.
'47. Beitrag zur Entwickelungsgeschichte der Samenkorperchen bei den Ne-
matoden. Arch. f. Anat. Physiol. u. wiss. Med., Jahrg. 1847, pp. 88 -
147, Taf. VI. 1847.
56. Ueber die Micropyle der Fischeier und tiber einen bisher unbekannten,
eigenthiimlichen Bau des Nahrungsdotters reifer und befruchteter Fischeier
VOL. VI.— NO. 12. 39 ‘
610 BULLETIN OF THE
(Hecht). Arch. f. Anat. Physiol. u. wiss. Med., Jahrg. 1856, pp. 83 -
124, Taf. II., III., und IV. Figs. 1-4. 1856.
Remak, Robert.
’55. Untersuchungen tiber die Entwickelung der Wirbelthiere. vi + xxxviii
+ 195 pp., 12 Taf. Berlin: G. Reimer. 1850, 1851, 1855.
Repiachoff, W.
'78. Ueber die ersten embryonalen Entwicklungsvorgange bei Tendra zoste-
ricola. (Dec. 1877.) Zeitschr. f. wiss. Zool, Bd. XXX., Supplem.,
Heft 3, pp. 411-423, Taf. XIX. 28 May, 1878.
Robin, Charles Philippe.
’62. Mémoire sur les phénoménes qui se passent dans l’ovule avant la seg-
mentation du vitellus. Jour. de la Physiol, Tom. V. No. 17, pp. 67-
109.: Jan. 1862. ie
62>, Mémoire sur les globules polaires de l’ovule et sur le mode de leur pro-
duction. Compt. rend. de lAcad. des Sci. Paris, Tom. LIV. pp. 112 -
116. 1862.
’62°. Mémoire sur la production des cellules du blastoderme sans segmenta-
tion du vitellus chez quelques articulés. Compt. rend. de l’Acad. des Sci.
Paris, Tom. LIV. pp. 150-153. 1862.
’62°, Mémoire sur les globules polaires de Povule. (Lua Acad. des Sci.
le 11 Jan. 1862.) Jour. de la Physiol., Tom. V. No. 18, pp. 149-190,
Pl. I1.-V. Apr. 1862.
62°. Note sur la production du noyau vitellin. Jour. de la Physiol., Tom.
V. No. 19, pp. 309-323. Juillet, 1862.
’62'. Mémoire sur la production du blastoderme chez les Articulés. (Lu a
Acad. des Sci. le 20 Jan. 1862.) Jour. de la Physiol., Tom. V. No. 19,
pp. 348-383, Pl. VII. July, 1862.
‘75. Mémoire sur le développement embryogénique des Hirudinées. Mém.
de Acad. des Sci. Paris, Tom. XL. 472 pp., 19 pl. 1875.
Russow, Edmund.
'72. Vergleichende Untersuchungen betreffend die Histologie (Histogra-
phie und Histogenie) der vegatativen u. sporenbildenden Organe u. die
Entw. der Sporen der Leitbiindel-Kryptogamen, mit Bericksichtigung der
Histologie der Phanerogamen, ausgehend von der Betrachtung der Mar-
siliaceen. (Presented Apr. 6, 1871.) Mém. de l’Acad. imp. des Sci.
de St. Pétersbourg, Tom. XIX. No. 1, vi + 207 pp., Taf. 1.-XI. 1872.
Salensky, W.
74°, Ueber den Bau und die Entwickelungsgeschichte der Amphilina Wagn.
(Monostomum foliaceum Rud.). Zeitschr. f. wiss. Zool., Bd. XXIV. pp.
991-342, Taf. XXVILTI.—-XXXII. 16 Sept. 1874.
76. Embryonale Entwicklungsgeschichte der Salpen. Zeitschr. f. wiss. Zool.,
Bd. XXVII. Heft 2, pp. 179-237, Taf. XIV.-XVI. 23 June, 1876.
Sars, Martin.
’37. Zur Entwickelungsgeschichte der Mollusken und Zoophyten. Arch. f.
Naturg., Jahrg. III. Bd. I. pp. 402-407. 1887.
MUSEUM OF COMPARATIVE ZOOLOGY. 611
Schenk, S. L.
'73. Die Hier von Raja quadrimaculata (Bonap.) innerhalb der Hileiter. (Sitz.
ungsb. d. k. Akad. der Wissensch. Wien, Mathem-naturw. Cl., Bd.
LXVIII. Abth. 1, pp. 363-374, 1 Taf. 18 Dec. 1878.
"74. Der Dotterstrang der Plagiostomen. Sitzungsb. d. k. Akad. der Wis-
sensch. Wien, Mathem-naturw. Cl., Bd. LXIX. Abth. 1, pp. 801-308, 1
Taf. 26 Mar. 1874.
74°. Entwickelungsvorgange im Hichen von Serpula nach der kiinstlichen
Befruchtung. Sitzungsb. d. k. Akad. der Wissensch. Wien, Mathem-
naturw. Cl., Bd. LXX. Abth. 3, pp. 287-301, 1 Taf. 1875.
'76. Die Vortheilung des Farbstoffes im Hichen wahrend des Furchungspro-
cesses. Sitzungsb. d.k. Akad. der Wissensch. Wien, Mathem-naturw. CL.,
Bd. LXXIII. Abth. 3, pp. 112-120, 1 Taf. 17 Feb. 1876.
77. Bemerkungen iiber den Keimfleck. Mittheilg. embryol. Institut zu
Wien, Bd. I. Heft 1, No. V. pp.55-61. 1 Feb. 1877.
Schleicher, W.
'78. Ueber den Theilungsprozess der Knorpelzellen. Vorlaufige Mitthei-
lung. (27 May, 1878.) Centralbl. f. d. med. Wissensch., Jahrg. XVI.
No. 23, pp. 418, 419. 8 June, 1878.
'78. Die Knorpeltheilung. Ein Beitrag zur Lehre der Theilung von Ge-
webezellen. (Aus dem histologischen Laboratorium in Gent.) Arch. f.
mik. Anat., Bd. XVI. pp. 248 - 302, Taf. XII.-XIV. 20 Dec. 1878.
Schmidt, Oscar.
51. Ueber die Entwickelung von Limax agrestis. Arch. f. Anat. Physiol.
u. wiss. Med., Jahrg. 1851, pp. 278-290, 1 Taf. 1851.
Schmitz, Fr.
'79. Beobachtungen tiber die vielkernigen Zellen der Siphonocladiaceen, pp.
273-320, Taf. XII. Festschrift zur Feier des hundertjahrigen Bestehens
der Naturf. Gesellsch. in Halle, a. 8., 342 pp., 12 Taf. Halle: Max Nie-
meyer. 1879.
Schneider, Anton.
'73. Untersuchungen tiber Platthelminthen. 14 Jahresbericht der oberhes-
sischen Gesellschaft fir Natur- und Heilkunde, pp. 69-140, Taf. ILI.
-VII. Giessen, April, 1873.
Schultz, Alexander.
‘75. Zur Entwickelungsgeschichte des Selachiereis. (Jan. 1875.) Arch.
f. mik. Anat., Bd. XI. pp. 569-582, Taf. XXXIV. 1875.
Schultze, Max Sigismund.
’65. Zur Kenntniss der Leuchtorgane von Lampyris splendidula. Arch. f.
mik. Anat., Bd. J. pp. 124-137, Taf. V., VI. 1865.
Schulze, Franz Eilhard.
'74*. Rhizopodenstudien, IJ. Arch. f. mik. Anat., Bd. X. pp. 377 - 400,
Pat 2 VI, AVIL. 1874:
'75°. Ueber den Bau und die Entwicklung von Sycandra raphanus, Haeckel.
Zeitschr. f. wiss. Zool., Bd. XXV., Supplem., pp. 247 -260, Taf. XVIII. -
XXI. 22 Dec. 1875.
612 BULLETIN OF THE
Schwalbe, G.
68. Ueber den Bau der Spinalganglien nebst Bemerkungen tiber die sympa-
thischen Ganglienzellen. Arch. f. mik. Anat., Bd. IV. pp. 45-72, Taf.
LVS) VAS68.
'76. Bemerkungen iiber die Kerne der Ganglienzellen. (May, 1875.) Jena.
Zeitschr., Bd. X. Heft 1, pp. 25-40, 2 Holzschn. 15 Feb. 1876.
Selenka, Emil.
75. Hifurchung und Larvenbildung von Phascolosoma elongatum, Kef.
Zeitschr. f. wiss. Zool., Bd. XXV. Heft 4, pp. 442-450, Taf. XXIX.,
XXX. 25 July, 1875.
‘76%. Zur Entwickelung der Holothurien (Holoth. tubulosa u. Cucumaria
doliolum). in Beitrag zur Keimblattertheorie. Zeitschr. f. wiss. Zool.,
Bd. XX VII. Heft 2, pp. 155-178, Taf. 1X.-XIII. 23 June, 1876.
78. Beobachtungen iiber die Befruchtung und Theilung des Kies von Toxo-
pneustis variegatus. Vorlaufige Mittheilung. (June, 1877.) Sitzsungsh.
d. phys.-med. Gesellsch. zu Erlangen, Heft X. pp. 1-7. 1878.
'78*. Zoologische Studien. I. Befruchtung des Hies von Toxopneustis varie-
gatus. in Beitrag zur Lehre von der Befruchtung und Eifurchung. vi
+18 pp. Leipzig: Wm. Engelmann. 1878.
Semper, Carl.
’57. Beitrage zur Anatomie und Physiologie der Pulmonaten. Zeitschr. f.
wiss. Zool., Bd. VIII. Heft. 3, pp. 340-399, Taf. XVI., XVII. 12 Nov.
1856.
"75. Ueber die Entstehung der geschichteten Cellulose-Epidermis der Asci-
dien. Arbeiten a. d. zool.-zoot. Institut in Wurzburg, Bd. II. pp. 1-24,
6 VTi Od SS
'75°. Das Urogenitalsystem der Plagiostomen und seine Bedeutung fir das
der ibrigen Wirbelthiere. Arbeiten a. d. zool.-zoot. Institut m Wirz-
burg, Bd. IL. pp. 195-509, Taf. X.-XXIT. 1875.
Spengel, J. W.
"76. Das Urogenitalsystem der Amphibien. Arbeiten a. d. zool.-zoot. Insti-
tut in Wirzburg, Bd. III. Heft 1, pp. 1-114, Taf. I.-1V. 1 July,
1876.
Stecker, Anton.
76°. Ueber die Entwickelung der Chthonius-Hier im Mutterleibe, und die
Bildung des Blastoderms. Sitzungsb. der k. bohm. Gesellsch. der Wis-
sensch. Prag., Jahrg. 1876, No. 3, pp. 122-135, 7 fig. 24 Mar. 1876.
"76°. Transl. by W.S. Dallas iz Ann. and Mag. of Nat. Hist., ser. 4, Vol.
XVIII. No. 105, pp. 197 — 207, 7 fig. Sept. 1876.
Stilling, B.
’56. Anatomische und mikroskopische Untersuchungen ttber den Bau der
Nervenprimitivfaser und der Nervenzelle. 11+ 152 pp.,2 Tab. Frank-
furt a. Main: J. Riitten. 1856.
’56—’59. Neue Untersuchungen iiber den Bau des Riickenmarks. Frank-
furt a. Main: J. Riitten. Cassel: H. Hotop. 20+ 1192 + 108 pp.
1856-1859.
MUSEUM OF COMPARATIVE ZOOLOGY. 613
Stossich, Michele.
"76. Sopra lo sviluppo delle serpule. Boll. Soc. Adriat. di Sci. nat., Vol.
IL. No. 3, pp. 276-282, Tav. I. 1876.
‘77. Transformazione della vescica germinativa e sua importanza nella seg-
mentazione del tuorlo. (9 July, 1877.) Boll. Soc. Adriat. di Sci. nat.,
Vol. III. pp. 212-239, Tav. L., IL.
Strasburger, Eduard.
"75. Ueber Zellbildung und Zelltheilung. (May, 1875.) Jena: Hermann
Dabis. 1875.
"76. Same. ‘Zweite verbesserte und vermehrte Auflage nebst Untersuchun-
gen iiber Befruchtung, 12 + 382 pp., Taf. 1.- VIII. Mar. 1876.
"76". Studien iiber das Protoplasma. Jena. Zeitschr., Bd. X. Heft 4, pp. 395
- 446, Taf. XIII., XIV. Oct. 1876.
77. Ueber Befruchtung und Zelltheilung. (Aug. 1877.) Jena. Zeitschr.,
Bd. XI. Heft 4, pp. 435 -536, Taf. XXVII.-XXXV. 10 Dec. 1877.
Stricker, S.
77. Beobachtungen iiber die Entstehung des Kerns. Sitzungsb. d. k. Akad.
der Wissensch. Wien, Mathem.-Naturw. Cl., Bd. LXXVI. Abth. 3, pp. 7
228. 7 June, 1877.
Torok, Aurel v.
"74. Rolle der Dotterplattchen beim Aufbau der Gewebe. Centralbl. f. d.
med. Wissensch., Jahrg. XII. No. 17, pp. 257-261. 4 Apr. 1874.
'77. Ueber formative Differenzirungen in den Embryonalzellen von Siredon
pisciformis. Hin Beitrag zur Histogenese des Thierorganismus. (23 Sept.
1876.) Arch. f. mik. Anat., Bd. XIII. Heft 4, pp. 756-783, Taf. XLIV.
S377.
Treub, M.
’'79. Quelques recherches sur le réle du noyau dans la division des cellules
végétales. Akad. van Wetenschappen, Amsterdam, Deel XIX. 35 pp.,
4pl. 1879.
Trinchese, Salvatore.
'76. Sulla rete protoplasmatica della vescicola germinativa. Rendiconto
dell’ Accad. Sci. dell’ Istit. di Bologna, Annata 1875-76, pp. 51,52. 13
Jan. 1876.
'76%, Anatomia della Caliphylla mediterranea. Mem. dell’ Accad. Sci. dell’
Istit. di Bologna, 3 ser., Tom. VII. fase. 2, pp. 173-192, 2 Tav. 30 Mar.
1876.
76. Sulla struttura della cellula animale. Rendiconto dell’ Accad. Sci.
dell’ Istit. di Bologna, Annata 1875-76, pp. 122,123. (See also p. 70.)
27 April, 1876.
'77, Sulla struttura dell’ uovo dei mammiferi e dei molluschi. Rendiconto
dell? Accad. Sci. dell’ Istit. di Bologna, Annata 1876-77, pp. 36, 37. (See
also p. 156.) 4 Jan. 1877.
Tschistiakoff, J.
'75. Beitrage zur Physiologie der Pflanzenzelle. Kurze Notizen und vor-
614 BULLETIN OF THE
laufige Mittheilungen iiber die Entwickelung der Sporen und des Pol-
lens. (14 July, 1874.) Botanische Zeitung, Jahrg. 33, Nos. 1, 2, 3, 6, 7,
pp. 1-8, 17-26, 83-38, 81—88)97 —103, Tata. 2,8; 16 Janieo ae
Feb. 1875.
Turpin, J. F.
32. Analyse microscopique de Pout du Limagon. Ann. des Sci. nat., Tom.
XXV. pp. 426-455. 1832.
Villot, A.
'74. Monographie des Dragonneaux (Genre Gordius, Dujardin). (4 Feb.
1874.) Arch. de Zool. exp. et gén., Tom. III. pp. 39-72, 181-238,
Pl Via ee VLU Xe alee
Vogt, Carl.
’42. Untersuchungen tiber die Entwickelungsgeschichte der Geburtahalfer:
krote (Alytes obstetricans), x +134 pp., 3 Taf. Solthum: Jent u.
Gassmann. 1842.
Wagener, Guido.
’57. Ueber den Zusammenhang des Kernes und Kernkérpers der Ganglien-
zelle mit dem Nervenfaden. Zeitschr. f. wiss. Zool., Bd. VIII. Heft 4,
pp. 455-458, Taf. XXI. 26 Feb. 1857.
Walter, Georg.
58. Fernere Beitrage zur Anatomie und Physiologie von Oxyuris ornata.
Zeitschr. f. wiss. Zool., Bd. IX. Heft 4, pp. 485-495, Taf. XIX. 20
Dec. 1858.
Warneck, Nicolas Alexander.
50. Ueber die Bildung und Entwickelung des Embryos bei Gasteropoden.
Bull. Soc. impér. des Naturalistes de Moscou, Tom. XXIII. No. 1, pp. 90
~ 194, Taf. Tl. -—TV., 1850.
Weil, C.
'73. Ueber die Befruchtung und Entwicklung des Kanincheneies. Wiener
medicin. Jahrb., Jahrg. 1873.
bstr. by W. Miller 72 Hofmann u. Schwalbe’s Jahresberichte, Bd. III.
p. 441.
Whitman, Charles Otis.
'78. Ueber die Embryologie von Clepsine. Zool. Anzeiger, Jahrg. I. No. 1,
pp. 5; 6.001 Paly, 2378: :
78°. The Embryology of Clepsine. Quart. Jour. of Mic. Sci., n. ser., No.
71, Vol. XVIII. pp. 215-315, Pl. XII.-XV. July, 1878.
Also separate, 101 pp. 4 pl. 1878.
"79. Changes Preliminary to Cleavage in the Egg of Clepsme. [Abstract. ]
(Aug. 1878.) Proc. Amer. Assoc. Adv. Sci., Vol. XX VII. pp. 263-270.
1879.
Pre-print, pp. 263-270. Salem. Feb. 1879.
Zeller, Ernst.
'76. Weiterer Beitrag zur Kenntniss der Polystomen. Zeitschr. f. wiss.
Zool., Bd. XX VII. Heft 2, pp. 238-274, Taf. XVII., XVIII. 23 June,
1876.
MUSEUM OF COMPARATIVE ZOOLOGY.
INDEX TO AUTHORS
Agassiz, A., 447, 516.
Agassiz, L., 253, 517.
Arndt, 257, 265.
Arnold, 270.
Auerbach, 254, 259-261, 280, 283-286,
304, 333, 344, 362, 370-372, 399 -
402, 469, 534, 540, 558, 564, 588.
Axmann, 256.
Baer, Von, 274, 388, 392.
Balbiani, 253, 275, 347, 396.
Balfour, 254-256, 306-308, 416, 457,
499, 512, 514, 524, 548, 554, 555.
Bambeke, Van, 198, 389, 402, 418, 474,
517, 518, 548.
Barrois; 425.
Beneden, Ed. van, 215, 254, 262, 275,
302-304, 312, 388, 411-415, 417,
473, 516, 549, 567.
Beneden, P. J. van, 390.
Beneden, Van, et Windischmann, 234 —
236, 390.
Benecke. See Kupffer und Benecke.
Bischoff, 331, 388, 390, 486, 549.
Blanchard, 467, 511.
Bobretzky, 313-317, 319, 340, 386, 425,
518.
Brandt, 237, 828 — 331, 334, 387, 442, 446.
Brooks, 411.
Biitschli, 177, 240, 249,
287, 289, 317-324,
349, 393, 395-397, 400, 403, 406,
420, 421, 430-434, 449, 468, 470,
472, 475-477, 5386, 549, 554, 556,
564.
254, 277 — 282,
332, 342-344,
Calberla, 455, 496 - 499.
_Campana, 479.
Carus, 245, 389.
Chun, 264.
Claparede, 249.
Courvoisier, 257.
Dallinger and Drysdale, 450.
Darwin, 555, 557.
Derbés, 245, 392.
Dieck, 397, 549.
Drysdale, 450.
Dujardin, 232.
Dumortier, 233, 389-391.
615
CITED IN THE TEXT.
Eberth, 258, 344-347, 359.
Himer, 250-254, 257, 267, 301.
Ewetsky, 342.
Flemming, 194, 254, 257, 264, 267, 268,
271, 278, 279, 281, 288, 305, 320, 351,
355-366, 370, 390, 397, 402, 514,
524, 549, 561, 588.
Feettinger, 349.
Fol, 177, 221, 237, 239-241, 254, 279,
286, 291, 298, 309, 324-327, 390,
396, 397, 402, 406-408, 422, 429,
435, 436, 439, 444-446, 471, 478-
480, 484-486, 488-491, 519, 521,
522, 545, 557, 558, 566 — 590.
Frey und Leuckart, 264.
Frommann, 257, 261.
Galeb, 334, 456.
Gegenbaur, 232, 235, 248, 248, 273.
Giard, 254, 332, 419, 448, 479, 485, 489,
DET:
Gibbes, 216.
Goette, 298 — 301, 405, 470, 512.
Greeff, 253, 419, 424, 478.
Grenacher, 253.
Grobben, 334, 547.
Grube, 245.
Haeckel, 288, 393, 410,. 472, 514, 516,
518.
Hanstein, 273.
Harless, 256.
Hatschek, 340, 450, 491, 514.
Heitzmann, 258.
Helm, 264.
Hemsbach, 253, 264.
Henneguy, 548.
Hensen, 473.
Hertwig, O., 177, 198, 248, 253, 254,
292-298, 319, 327, 339, 408-410,
421, 422, 427, 431, 433, 434, 436-
442, 446, 452-455, 464-467, 471,
474, 480-483, 495, 506, 509-511,
514, 518, 519, 529, 536, 540, 541,
545, 548, 550, 553, 569.
Hertwig, R., 254, 263, 265, 540.
His, 289.
Hoek, 549.
616
Hoffmann, 254, 333.
Hofmeister, 366, 450, 491.
lijima, 535.
Jhering, Von, 335, 410, 499.
Klebs, 263, 341.
Klein, 256, 270.
Kleinenberg, 254, 395, 427.
Kolliker, 252, 276.
Korotneff, 395, 427, 434.
Kowalevsky, 249, 276, 301, 516, 517.
Krohn, 246, 392.
Kupffer, 249, 258, 411.
Kupffer und Benecke, 459, 501-508, 518.
Lang, 340.
Langerhans, 258.
Langhans, 265.
Lankester, 232, 286, 395, 397.
Laurent, J. L. M., 232, 233, 235.
Laurent, P., 232.
Lavdowsky, 265.
Leuckart, 249, 264, 392.
Leydig, 216, 252, 264, 275, 390, 547.
Lieberkiihn, 256.
Loven, 274, 390, 391, 514.
Ludwig, 309, 410, 419.
McCrady, 329, 487.
Mark, 173.
Mayer, P., 264, 332, 382, 447.
Mayer, S., 258.
Mayzel, 244, 341, 348, 349, 859, 558,
559.
Meckel von Hemsbach, 2538, 264.
Meissner, 246, 248, 273.
Metschnikoff, 275, 282.
Minot, 486.
Miiller, A., 393.
Miiller, Friedrich, 390.
Miiller, Johannes, 274.
Miiller, P. E., 464.
Munk, 248.
Oellacher, 251-253, 287, 288, 389, 394,
517, 518, 548.
Peremeschko, 351.
Pérez, 244, 483, 489, 558, 559 — 566.
Pfliiger, 251.
Priestley, 295, 304, 424.
Purkinje, 388.
Quatrefages, 246, 392.
Rabl, 313, 410, 425-427, 514, 516, 556.
BULLETIN OF THE MUSEUM OF COMPARATIVE ZOOLOGY.
Rathke, 553.
Ratzel, 276, 393.
Ratzel und Warschawsky, 393.
Reichert, 246, 250, 392, 517.
Remak, 247,
Repiachoff, 335, 458.
Robin, 197, 390, 416, 473, 564.
Russow, 279, 366-368.
Sachs, 273.
Salensky, 283, 424.
Sars, 235.
Schenk, 283, 397, 399, 435.
Schleicher, 352-355.
Schmidt, 232.
Schmitz, 380.
Schneider, 249, 278, 279, 283, 395.
Schultz, 252.
Schultze, 252.
Schulze, 253, 415, 518.
Schwalbe, 257, 262.
Selenka, 297, 333, 336-338, 406, 424,
450, 458, 492-494, 499-501, 520.
Semper, 252, 255, 342, 411.
Spengel, 264.
Stecker, 411, 419.
Stilling, 256.
Stossich, 325, 423, 427-429, 448, 488.
Strasburger, 266, 279, 292, 301, 305, 306,
308-311, 344, 348, 350, 363, 370, ©
372-385, 411, 419-424, 450-452,
477, 494, 547, 554, 556, 564, 589.
Stricker, 268 — 270.
Torok, 266.
Treub, 385 — 387.
Trinchese, 254, 255, 262.
Tschistiakoff, 368-370, 380.
Turpin, 232.
Van Bambeke. See Bambeke.
Van Beneden. See Beneden.
Villot, 387, 397.
Vogt, 253, 261.
Von Baer. See Baer.
Wagener, 256.
Walter, 249.
Warneck, 177, 220, 234-2438, 274, 330.
Warschawsky, 393.
Weil, 468.
Whitman, 197, 247, 254, 282, 301, 338,
411, 421, "422, 460 - "464, "487, 503 —
509, 513, 516, 518, 524, 535, 547,
556, 557. .
Windischmann, 234 — 236, 390.
Zeller, 311, 424.
EXPLANATION OF FIGURES.
618 BULLETIN OF THE
LETTERS.
THE following letters are used throughout to designate respectively : —
A. A = Amphiaster. Pv = Purkinjean vesicle.
Al = First archiamphiaster. pz = Clear zone in the yolk.
A? = Second archiamphiaster.
4 = Amphiaster of first segmenta- | R. r = Polar globule (Richtungs-
tion sphere. blaschen).
@ == Aster. rv! = First polar globule.
aa == Central area of aster. r/’ == Second polar globule.
aa’ = Structures at the centre of aa. rv == Nuclear structure of r.
ae == External aster. rnt = Nucleolar structure of r.
ai = Internal aster.
ar = Rays of aster. S. sp- = Nuclear spindle.
ar! =$Thickenings in ar. sp! ==: First maturation spindle.
ars = Spiral aster-rays. sp» == Second maturation spindle.
sp? = Spindle of first segmentation
F. fpn = Female pronucleus, sphere.
Jpnl = Female pronucleolus. spf = Spindle fibres.
spf! == Interzonal filaments.
M. ma = Male aster. spf!!/= Thickenings in spf! (Zell-
mpn = Male pronucleus. platte 7).
mpnl == Male pronucleolus. spl == Lateral zones of spindle
thickenings.
N. 2 = Nucleus. spm = Median (equatorial) zone of
spindle thickenings.
Pp = Pedicel, or neck of polar spz == Spermatozoa.
globule.
pn, pn! = Pronuclei. Vi. V,, = Vitellas.
pnt = Pronucleoli. ve == Vitelline envelope.
pp = Pedicel-plate (Zellplatte ?). vm = Vitelline membrane.
TREATMENT, ETC.
All Figures, except 62%, 94, and 95, were drawn with the aid of the Chevalier-
Oberhauser camera; and all, except 80°, 80°, and 95, relate to Limax campestris.
Figures 1-21, 27, 49, 51, 62%, 65, 70°, are magnified 140 diameters; Figs. 30-
38, 76, about 200 diameters; Fig. 95, 300 diameters; all other Figures 750
diameters.
The following Figures were made from living eggs: 1-21, 27, 30-38, 49, 51,
62°, 65, 70*, and 95.
Figures 28, 29, 44, 52, and 52%, are from sections of eggs hardened in chromic
acid ; all others, except Figs. 26 and 76, from the egg entire.
Osmic acid (1%), followed by carmine, was employed to harden and stain those from
which Figs. 63, 64, 68-70, 71, 72, 75, and 77, were drawn. Those of Figs. 69 and
75 remained unstained by Beale’s carmine.
All eggs not otherwise specified were treated with acetic acid (1%-2%) for three
hours or more, and were subsequently stained in Beale’s carmine.
. MUSEUM OF COMPARATIVE ZOOLOGY. 619
PLATE I.
Figs. 1-20. Formation of polar globules.
Figs. 1-9. Successive views of the same egg at 6:00, 6:02, 6:04, 6:06, 6:30,
7:40, 9:30, 10:45, and 11 o’clock.
Figs. 10-14. Formation of second polar globule. Another egg seen at 11:08,
11:09, 11:10, 11:12, and 11:15 o'clock.
Figs. 15-20. Formation of second polar globule as seen in another egg, at 6: 08,
6:33, 7:04, 7:05, 7:06, and 7:15. First segmentation of this egg nearly completed
at 10:00 o’clock.
Fig. 21. Egg showing an irregular zone of clear protoplasm and two pronuclei.
Fig. 22. The deeper of the lateral zones of fibre thickenings has reached the
border of the well-defined central area of the internal aster. Optical meridional
section.
Fig. 23. Optical section in the plane of the polar globule, showing the second
archiamphiaster ; the peripheral aster more sharply outlined than the deeper one.
Fig. 24. Same seen along the axis of the spindle. Focused a little above the
centre of the superficial aster ; the polar globule ‘‘ projected.” (Its outline has been
made too irregular and ragged in lithographing. )
Fig. 25. Another egg of about the same stage, and seen in the same position as
Fig. 22.
Fig. 26. Yolk elements from the vitellus of a crushed egg.
Fig. 27. Peculiar appearance, as of decussating fibres, seen at the animal pole
after the formation of the first polar globule.
Figs. 28, 29. The fourth and third respectively of five successive sections of the
egg, Fig. 21, put in acid during the first segmentation. Slightly distorted by the
traction of the knife in cutting. The plane of section is not quite parallel with the
plane determined by the polar axis and the line joining the centres of the two asters,
but cuts both these lines. From its obliquity to the polar axis, it results that the
polar globules, and the curved remnant of the spindle (interzonal filaments), which
both lie in this axis, are found not in the same but in successive sections. From its
obliquity to the line joining the astral centres, it results that the nucleus of one of
the two segmentation spheres is cut, as shown in Fig. 29, while the other remains
untouched, and also that the interzonal filaments (spf’’) are cut across in the sphere
“marked ‘‘y” (Fig. 29). Chromic acid preparation.
Figs. 30-32. Three successive views of an egg, at 8, 8:54, and 9 o’clock.
Fig. 30. Polar globules already formed. The two pronuclei with very clear cir-
cular outlines of nearly equal size. No change from the spherical form observed.
Fig. 31. The egg has changed form slightly, and two oval, ill-defined spots are
visible, at some distance apart, the pronuclei having disappeared. The yolk shows
a faintly expressed radial arrangement of granules about these two spots.
Fig. 32. The spots are farther apart; the radiate arrangement more distinct ; the
cleavage furrow at the animal pole of the yolk is quite pronounced.
Figs. 33-385. Three views of an egg, at 7:54, 8:35, and 9:12 o'clock.
Fig. 33. A clear spot at the animal pole, and deeply penetrating narrow zone of
clear protoplasm (pz) near the equator.
620 BULLETIN OF THE
Fig. 34. The clear spot has moved to near the centre of the egg; the equatorial
zone is less distinct.
Fig. 35. The first segmentation furrow has already extended to the vegetative
pole. .
Figs. 36-38. Three views of the same egg, at 8:10, 9:04, and 9:15 o'clock.
Fig. 36. Male and female pronuclei, and equatorial clear zone (pz) visible, the
latter intermediate in prominence between that of Figs. 33 and 34.
Fig. 37. Beginning of the first segmentation of the yolk. The pronuclear struc-
tures have disappeared, and the oval spots, from the position of the egg, partly cover
each other.
Fig. 38. Near the close of the first segmentation.
PLATE II.
Fig. 39. Optical section of an egg, showing the first archiamphiaster, and pe-
ripheral clear areas in the yolk.
Fig. 40. Optical section of an egg and first polar globule, with lateral zones of
thickenings, prominent interzonal filaments, and possible indications of an ameboid
character of the yolk at the animal pole.
Fig. 41. Surface view of the polar globule of the same.
Fig. 42. View of same globule, the optical axis coinciding with the primary (ani-
mal) radius of the egg. It shows the annular arrangement of the spindle thicken-
ings, and the outline of the pedicel.
Fig. 43. First archiamphiaster. The external aster causes a protuberance at the
surface of the yolk, and exhibits a highly refractive body at the centre of radiation.
Nuclear spindle inconspicuous ; equatorial thickenings not prominent.
Fig. 44. Section of an egg just before the first segmentation. The plane of sec-
tion is parallel with the axis of the spindle. About one third of the spindle was cut
away by the section preceding the one here represented. A highly refractive spherical
body occupies the centre of each of the astral areas, and the thickenings of the spindle
fibres are arranged in two closely approximated parallel zones. !
Fig. 45. First ‘archiamphiaster at the time the rays of the external aster attain
the surface of the yolk. The external aster is more sharply outlined than the in-
ternal. The first maturation spindle presents only a single (equatorial) zone of fibre
thickenings. The flattened appearance of the animal pole is probably due to the
resting of the yolk on that pole during its preparation, and while still incompletely
hardened.
Fig. 46. Equatorial optical section of the same; the spindle thickenings are
projected, and exhibit the usual annular arrangement.
Fig. 47. External aster of same; the optical axis coinciding with the axis of
the spindle. The rays have a spiral course.
Fig. 48. The first archiamphiaster has approached the animal pole still more
closely than in Fig. 43. The external aster has thereby become more conspicuously
unsymmetrical. The spindle is more distinctly marked, and shows the equatorial
zone just dividing into its lateral halves. Both asters exhibit large areal corpus-
cles. The “halos” around each should be narrower ; more as in Fig. 43.
Fig. 49. Living egg at the close of the formation of the first polar globule. Radi-
MUSEUM OF COMPARATIVE ZOOLOGY. 621
ate markings at the clear animal pole of the yolk. Numerous highly refractive
spermatozoa in the vicinity of the vitellus.
Fig. 50. First archiamphiaster has migrated still farther than in Fig. 48 toward
the animal pole, the centre of the external aster having nearly attained the surface of
the yolk. The conical protuberance caused by ae is covered by a cap of finely granular
substance (compare text, p. 198). Lateral zones of spindle thickenings half-way
between the equator and the poles of the spindle.
Fig. 51. A single ill-defined clear spot seen in the living egg, where the pronuclei
are found in the ‘same egg hardened and cut (Figs. 52, 52"). Equatorial zone of clear
protoplasm, pz.
Figs. 52, 52%. The third and fourth of five sections through the egg, shown in
Fig. 51, the egg having been put in chromic acid immediately after the outlines
(Fig. 51) were made. Both pronuclei contain numerous.nucleolar bodies joined by
irregular fibres, which thus produce an indistinct reticulum.
In Fig. 52 are to be seen the two polar globules, nearly the whole of the female
pronucleus, a portion of the male pronucleus, and, near the border of the latter, an
incipient aster of 4%, with a conspicuous highly refractive structure (aa’) occupying
the centre of the astral area.
In Fig. 52° is seen the remainder of the male pronucleus. No other aster had as
yet made its appearance in the yolk.
PLATE III.
Fig. 53. Archiamphiaster, whether the first or the second is uncertain. Con-
sult text at pp. 189, 206.
Fig. 54. Another view of the same. The optical axis coincides with the axis of
the incipient spindle. The nuclear substance, largely accumulated on one side of
the spindle, is seen as though ‘‘ projected” on the equatorial plane passing through
the centre of the internal (deeper) aster.
Fig. 55. Second archiamphiaster. The spindle exceptionally slender. The yolk
about the animal pole is constricted by two or three rings, which give it a wavy out-
line when seen in optical section. Compare with the description of the formation of
polar globules in Clepsine, as given by Whitman (78%, pp. 232, 233, and separate,
pp. 18, 19, Pl. XII. Figs. 2-6).
Fig. 56. Equatorial optical section of same. The external aster with spiral rays
projected ; optical axis slightly inclined from the spindle axis.
Fig. 57. Internal aster of the second archiamphiaster, with compound curvature
of rays. Male and female pronuclei; the centre of the aster nearer the latter.
‘*Interzonal filaments,” exceptionally prominent, unite the second polar globule to
the vitellus. A thin pellicle (vitelline membrane ?) stretches over the second polar
globule, the first having become detached. Granulations of the yolk omitted.
Fig. 58. Male and female pronuclei, the latter near, but not coinciding with, the
centre of the inner aster of the second archiamphiaster. In this figure only that por-
tion of the inner aster is shown which lies very near the surface of the yolk, the rays
of which are stout and nearly straight. The centre of the astral areais occupied by a
few granules not quite so conspicuous as the pronucleoli, and certainly not embraced
within the outline of the female pronucleus, which is well marked. Compare Fig. 78
or deeper portions of this aster.
622 BULLETIN OF THE
Fig. 59. Yolk of exceptional form. The primitive axis lies in the plane of the
optical section. The pronuclei, male and female, have attained considerable size, the
latter still united to the polar globule by interzonal filaments. About midway between
the pronuclei a dense, but less granular area, around which the yolk granules show a
radial arrangement, —the senescent internal aster of the second archiamphiaster.
The region of this aster is more deeply stained than the surrounding yolk. Another
region of crescentic form appears in the vegetative half of the yolk beyond the male
pronucleus, and is likewise deeply stained. It is represented in the figure by deeper
shading.
Fig. 60. Optical section oblique to the primitive axis. Polar globule ‘“‘pro-
jected.” Male and female pronuclei, the latter distinct -from the central area of the
internal half of the second archiamphiaster.
Fig. 61. Equatorial optical section. Polar globules, pedicel, lateral zone of thick-
enings, granules of astral area, and short stout rays of aster, projected. Granulation
of the yolk omitted. A sufficient difference in the prominence of the long and
the short rays has not been observed in lithographing.
Fig. 62. Meridional optical section of same, the first polar globule being omitted.
Lateral zone and areal corpuscles more nearly approximated than usual.
Fig. 62°. Living egg near the close of the first segmentation. Consult the text
at p. 223.
Fig. 68. Female pronucleus small, homogeneous, lying at the border of the cen-
tral area of the internal aster. The ‘‘interzonal filaments” exhibit a plate, pp (the
Zellplatte ?), near the point of their deepest constriction. The areal corpuscle of the
external aster fused with the envelope of the polar globule at its distal pole. Osmic
acid preparation.
Fig. 64. The second polar globule of the same egg seen from the animal pole.
Osmic acid preparation.
Fig. 65. The male and female pronuclei in the living egg.
Fig. 66. Formation of the second polar globule; ‘‘interzonal filaments” bent
nearly at right angles (compare Fig. 19) ; the spiral rays of the internal aster radiate
from a spiral line, a8; the areal corpuscles and the thickenings of the internal zone
not distinguishable from each other ; two vesicular structures in the vegetative hemi-
sphere — incipient male pronuclei (?) —do not contain nucleolar corpuscles.
Fig. 67. Portion of the same egg seen after rotating the yolk 90° about the
primitive diameter as an axis. The internal end of the spindle is deeply stained, but
not sharply defined.
PLATE IV.
Fig. 68. Second polar globule with nucleus, and longitudinal folds in the en-
velope of its pedicel. The position of the vitelline half of the “interzonal filaments ”
ig indicated by a streak of non-granular protoplasm extending to the female pro-
nucleus, in which, however, filaments are not traceable. Both pronuclei pear-shaped,
with the sharper ends (not outlined with sufficient distinctness) directed toward the
centre of a clear spot which is surrounded by numerous faint rays, —the senescent
internal aster of the second archiamphiaster. The pronucleoli more numerous in
the female (25) than in the male (20) pronucleus. Osmic acid preparation.
Fig. 69. Oblique view of the formative pole of the yolk (the two polar globules
'
MUSEUM OF COMPARATIVE ZOOLOGY. 623
omitted), showing male and female pronuclei, in which no nucleolar structures are
discernible. An invagination of the yolk into one side of the female pronucleus is
compensated by an evagination of the wall of the latter into the substance of the
male pronucleus. Compare Fig. 75. Osmic acid preparation.
Fig. 70. Pronuclei. The position of the internal aster of 4? is indicated by the
irregular non-granular area near the female pronucleus, but no radial differentiation
can be distinguished. The pronucleoli of about the same number (15 and 16) in each
of the pronuclei. Osmic acid preparation. Compare Fig. 72.
Fig. 70%. Living egg. Recession of the granular yolk from the surface, especially
at the primary'pole, which lies a little to the left of the polar globules.
Fig. 70°. Early stages in the formation of the pronuclei: a, the female pro-
nucleus; 8, the male.
Fig. 71. Second polar globule of the egg shown in Fig. 72 with two nuclear
structures, as seen after rotation about the primitive diameter as an axis. Osmic
acid preparation.
Fig. 72. Meridional optical section. The pronuclei large, considering the dis-
tance between them. The centre of the senescent internal aster of 4? nearly coin-
cident with the centre of the female pronucleus, ‘as shown by the course of the faint
rays still traceable. Osmic acid preparation. See also Fig. 70.
Fig. 73. Pronuclei still unconsolidated after the appearance of one of the asters of
the amphiaster of the first segmentation sphere. Nucleoli numerous. No trace of
the complementary half of this amphiaster discoverable. Compare Fig. 80.
Fig. 74. Both asters of A? extensively developed ; one distant from the female
pronucleus, which still remains unfused with the male pronucleus, although in con-
tact with it.
Fig. 75. A deep cup-shaped invagination of the yolk has forced inward one side
of the female pronucleus, and a slight projection from the opposite side of the latter
is plunged into the male pronucleus. Both present a wrinkled appearance, but no
trace of nucleolar structures. Osmic acid preparation. Compare Fig. 69.
Fig. 76. -Yolk crushed after the formation of the amphiaster of the first segmen-
tation sphere. The spindle is proportionately somewhat shorter than before the yolk
was crushed. Slender strings of protoplasm stretch from the spindle to one of the
fragments of an aster.
Fig. 77. The two pronuclei near the primary pole, each containing about a dozen
nucleoli. Those of pn/ are shaded to distinguish them from those of yn. No trace of
either aster. Osmic acid preparation.
Fig. 78. Equatorial optical section of the egg shown in Fig. 58. The outlines
of the polar globule and of the two pronuclei ‘‘ projected.”’ The superficial rays
and the granulations of the yolk are omitted, so as to show better the spiral course
of the numerous deep rays. Seen from the primary (animal) pole. Consult text,
p. 209.
Fig. 79. Pronuclei seen from the primary pole, each containing about thirty
pronucleoli. Only one aster of 4? discernible. Pronuclei not confluent.
Fig. 80. The ege which is exhibited in Fig. 73, so rotated that the face of the
pronucleus nearest the aster appears in profile. The centre of the aster lies at some
distance from the sharp outline of the pronucleus.
Fig. 80% Egg near the close of the second segmentation. The outlines of two of
the blastomeres, and partial outlines of the other pair, as seen from the secondary
624 BULLETIN OF THE
pole. Compare the shape of the nuclei, and the relation to their respective asters,
with that of the pronuclei in Fig. 68. The more pointed ends of the nuclei are
directed obliquely away from the observer, and the interzonal filaments, which are
much thicker in the middle than toward the ends, are so bent as to present to the
observer their convexities.
Fig. 80°. Nearly meridional view of the “ primary” half of an egg from an
undetermined species of Limax. Each pronucleus contains a single nucleolar struc-
ture which greatly exceeds any of the others in size; it is indicated by its shad-
ing, the remaining nucleolar bodies being only outlined.
Fig. 80°. The second polar globule of the same egg as that last figured, seen in
profile, to show the relation of the vitelline membrane, detached by the hardening
reagent, and the interzonal filaments to both polar globule and yolk.
Fig. 81. Vitellus showing one extensive aster with a homogeneous centre (female
pronucleus ?), the rays of which are numerous and slender, and several other less
extensive asters with few stout rays. The latter are probably induced by the pene-
tration of a corresponding number of spermatozoa into the yolk. Abnormal condition.
PLATE: V.
Fig. 82. Third amphiaster (43) after the almost complete disappearance of the
pronuclei. A few exceedingly faint outlines (pni?) may possibly be traces of pro-
nucleoli. An irregular plane of prominent granules (incipient nuclear plate ?) sepa-
rates the halves of the amphiaster. Asters flattened in the direction of the axis of the
still incomplete spindle. Thickenings (a7’) occur near the central ends of many of
the rays. The central areas contain numerous prominent granules (aa’). Compare
with Fig. 85.
Fig. 83. Amphiaster of the first segmentation sphere, with very prominent
spindle and equatorial zone of fibre thickenings (spm), the latter shown in
Fig. 84, as they appear when the optical axis corresponds with the axis of the
spindle.
Fig. 85. View from the secondary (vegetative) pole. The asters of A® well
developed before the complete union of the pronuclei. A few highly refractive
granules near the axis of the future spindle (too prominent in the engraving). One
of the astral areas is homogeneous, the other contains granules. The rays of the
asters present thickenings forming a zone concentric with the area. The external
limits of the thickenings are not sufficiently defined. The zones, interrupted two or
three times by the absence of thickenings from several neighboring rays, are not
quite accurately reproduced.
Fig. 86. A nearly face view of the amphiaster of the first segmentation sphere.
A remnant of the substance of the pronuclei is still visible between the spindle and
the animal pole. :
Fig. 87. The egg shown in Fig. 86, seen lengthwise of the spindle. The re-
mains of the nucleus are more distinct than in the preceding view. No fibre thick-
enings (nuclear plate) observed. Compare also Figs. 88 and 89.
Fig. 88. A slightly more advanced stage than is shown in Figs. 86, 87. The
asters nearly cover each other, the line of vision being almost parallel with the
spindle axis. The remnant of the nucleus, still sharply outlined, lies near the animal
pole, and is surrounded with a narrow zone of non-granular protoplasm.
MUSEUM OF COMPARATIVE ZOOLOGY. 625
Fig. 89. The same egg as the last, rotated nearly 90° about its primitive axis.
The remnant of the nucleus appears less sharply outlined. The elements of the
equatorial nuclear plate are very evenly arranged, and conspicuous.
Fig. 90. A slight furrow introducing the first segmentation of the yolk has made
its appearance at the animal pole. A vitelline membrane is detached from the yolk
over a space corresponding to this furrow. The nuclear spindle is viewed somewhat
obliquely, so that the lateral disks of fibre thickenings are not seen exactly edgewise,
and therefore appear oval. The left-hand edge is represented in the lithograph as
farthest from the observer ; the right-hand edge of the oval should have been made
the fainter, as it is really the more remote.
Fig. 91. Constriction further advanced than in Fig. 93; nuclei much larger ;
interzonal filaments distinguishable only near the plane of division between the two
secondary cells. Asters becoming less distinct.
Fig. 92. Equatorial thickenings in the spindle of the first segmentation sphere,
as seen when the spindle is viewed lengthwise.
Fig. 93. Formation of the nuclei of the first pair of blastomeres. Interzonal fila-
ments sharply bent and slightly thickened. Compare Fig. 29.
Fig. 94. Spermatozoon with vibratile (?) membrane. The tail end should have
been made thinner. The free edge of the membrane indicated by the sinuous line.
Fig. 95. View of a portion of a living egg of Limax sp.? toward the end of the
formation of the second polar globule, to show the existence of pseudopodia.
—
—t
0
Mus.Comp.Zoél\
ull
?
@]
t
1
e
E.L.Mark,d
oS
AEN ance
ae
1, VL
0
al\
Bull.Mus.Comp.Z06
L.Markdel.
E
Limax.
Figs: 39 3520.F il
e
A Meisel, lith
F
Bull.Mus.Comp.Zo61 Vol. VI.
PINS 4
Peano iey
Sp Ee
E.L.Mark del
{
ie
iS
{
\
CALE
a
we,
¥
o5
oc
oe a
£
pects
—
=z
Figs. 53-67, FLA.
Limax.
+]
Meisel, lith
A
Bull.Mus.Comp.Zool Vol. VI.
cee cee
igs. 68-81, Pl WW,
Bull.Mus.Comp.Zodl Vol. VI.
E.L.Mark del
2s
S25
¢
“.
¥
SCAR ARE we hs APR B® O57
QL Harvard University. Museum
of Comparative Zoology
haar Bulletin
web
| Biological
| & Medical
Serials
PLEASE DO NOT REMOVE
CARDS OR SLIPS FROM THIS POCKET
eR EAU ort LENE RO
UNIVERSITY OF TORONTO LIBRARY
| sas ea
- a a a er a Pe ee ae * peters gn 44 hart gt eee ae ee ee
n — Nana :
a" Cd prxtemge a - 7
> — f —_ os i a ples: al . a oS te ie eae
~~ —" ~~ ee ae tee Os ~ --_ - eral ee 7 -
— —_ hon w a a mR te re ew -” ine a
_ ~ or Seep ~~ ~ gy ng ge, RR 6 a en — a a OA PLLA. LIK
- ~- s es ae a a ~ a - Said
——e ~— dee — -— ~™ « ~ — ¢ ENE Oe er ee
ele — — ~ ~ a, tend Se es a aed
~ foe - - ° - ——er ere we en ee ee ee renee’
7 = _ —_ -_~ ~ ls a Cok een 9 # “ “
“ - ~ - > - — ~ i Ee ee Oe eee -
=: : _— — = ae OO ay a ie I ot em NE ne en eee
, ~ “ - a een: eg - COO A NA GOOG
on im - sehm a nd ae > ae “A -——
= % “a S ~~ ~~ > oe ee ee — ws
- - - -” ~~ On A oe gen et aN ewe
7 pe ~~ — _—_ - -# - a ee ee <r . arte
- ™ a « = nde teil om eg ae eto TP
ane ee am ee as —s - . paren tm
~ ' ah ~~ ~ — a ee ee — taco - as
* 4 Rete sg 6 ey 2 - ee ms to ate Aten - gm ai
7 ih ate — ee ee ee et tee ee Se eee ee —_—— _——- ~ eee
- ~ ” me eee oe — - ~~ _ o Cg =p a IT
_ oni ~ a (_—e S ieeien ielieal a. I — Se ee ee
~ ~* on pen = ~~ 5 eee een ee <2 oe as TT aa
o - —— ~ al diated a ~ ae pe ph a LO Se ae oe ee gg
ae - z ame —— ne EOE Ee, ok er Sey tet = a ee
—— - - ym — D< doe. sh, ines —— he oe ee ene my aye mo
- ad -_<—— oiie ~* wee ee) Oe OSes er a ee eee
=. -_ -_~< = —— | aad oo )- am - —-_— 5 ee ge ee Ee - a —_— =
7 — =—eoue = ey : TS fe a ee ens ae ns nr a at AN SO
_— ete a - ~~ = Ope “ remem ee er Te er Serer i le ete te
aoe Sa eye ee ce ee tee . ri ~a= ee ~ — et Amt gern, ee
od _ vis ye ¢ « ps - mi 4657 8 ee _—— - Preanne our RR pg
~ cal - A ow — ~~ a 4¢ pare ———— er —— = _ y= | eee _—
an ae se OT eat te, SP = oem on ake wt eo ee “ee er er ome Ue I a ne Se oe
—ert- “4 i i ~— + iat ation allie oad pee me an ~~. - “= °. et Po ea
ad ol wer RS ON ee OS i me ee ~ — eet yw gee Se n— et ~~ er om “a i ad tm fear
seme ee ——- ~~ . - ~ = th eaaell oe Siegal a “. “= Sm “
_ Wrenreres = ere ee Pept sire inlgin. om ie at = an — osm a See ee
+ id ee RL ee “= - ~ oe ee em we oe eS ee ee ee RE OTL Sar eran 1s
_ > ORE en Ry ey Vey Mee OE Re ma ~ _— we Sei es Pe eg mpm af = obama Me 0
ietend 2 ~~ ~ ee ee 7 _——_—~ > - = eer a mprenrmes yus Segnig
_ es ee = ~4 ~ Serengwese = + - ~ ee ee ae
NE RES Pere em 2 eC ae ee yee Sa re ae ~— ~ er
~ —-pee e ee a dat a a a Te ae - : Ci tee pe a
~ en Ee Te wy ~~ lt ee eee ere opel ae ge ST Rn ee ose - ee re “ 7
cary ter ae = 8A ern _— ne et ptm, tee —— = Ae - ~ Be, + re a ae et oy
_ ee om, re Rt Sle gene me et ew ee pe A meme ere es a pa
par vee “ae _~ ~~ oe - ee ET od Sm, ty my ining, i ee Spe ee
ane =" tel RS ee yer EE te ee ~~ ne oe eS ey = eg reve gmere
_— sews en nee tees _ ae Vv eee ot on een A ae = ee ns oe =e ee
- > ye ~ ~- ———— — nee ee + eS 9 =e <p en See
ti ndlnedaninan deed aed ~ So Te et ge gee ot - - a ~ ees et aes =) ee
a” cin ~- ~ en 8 eee ee oe ~~ rr ~—e o ~e Qrnae Ss
sitlindibesindn cntncniieontiee ean oe, a at ~ ae - an! ad ~ ot - el eee
= come ime a ete ee ee ag nanan ie Ral CS ee ne ee he erry ~ " a
pee sacl ee alow — Sle os ey eo ee eee. -
~s te Se My me . 7 we ee eo te wayne <~- ~we— py A a nk Net a ae NS me ee. ae
1a Ae OM, ign GR Hot EE ER A ene — AE Sitar marta a et SERRE de sre my REE om te PR A BF iit eRe - dee ee NE om
as te Ne ee TE meg ge Se ee tg mr mn tae a nF yg ay AL a RA el a OE RL ory oe oe
pt Re REO Rl PE MNT * 7 pg ee Ue RS <I epee tite ere ef Pe rh -— A ” ~
ON EE Re ey hee Se aa " ene —
patent Pe te a se ae ae oe een eR ee eee pert af eyo Se EEE nny te ee Re ym aw ym am he
Live Music
Archive
Librivox
Free Audio
Metropolitan Museum
Cleveland
Museum of Art
Internet
Arcade
Console Living Room
Open Library
American
Libraries
TV News
Understanding
9/11